New connection API and jack-in rewrite (#2324)

Second attempt on #2069. A brief description of the new functionality follows.


1) __Jack-in/connect__ 
  
   - User level commands:
  
     Create new sessions:
     
      C-c M-j: cider-jack-in-clj
      C-c M-J: cider-jack-in-cljs
     
      C-c M-c: cider-connect-clj
      C-c M-C: cider-connect-cljs
     
     Add new REPLs to the current session:
     
      C-c M-s: cider-connect-sibling-clj
      C-c M-S: cider-connect-sibling-cljs
 
   - `cider-jack-in-clojurescript` no longer creates two repls, only the cljs repl
  
   - clj repl has no longer a special status of the "main" repl. All repls within a session share same server and are siblings of each other. You can create as many clj and cljs siblings as you want from any repl. 
    
   - Creation of the client is no longer tightly bounded with the nrepl-server startup. The dynamic communication mechanism between jack-in and nrepl-server filter has been replace by a simple `on-port-callback`.
    
2) __New Connection and Session Management API__
 
   - Connections (aka REPLs) are grouped in [sesman](https://github.com/vspinu/sesman) sessions. Sibling repls are added to the current session.
  
   - Cider connection commands (`cider-quit`, `cider-restart`, `cider-display-connection-info`) have been refactored to operate exclusively on the connection level.
    
   - Sesman commands operate on the whole session:
  
     ![sesman-map](https://user-images.githubusercontent.com/1363467/41355277-6864ffb8-6f21-11e8-9387-3de586477d68.png)
   
   - Associations (links) between current context (buffer, directory, project) are governed by sesman and could be formed only on the session level. 
    
     In a nutshell, session can be linked to projects, directories and buffers. Buffer link have precedence over directory links, and directory have precedence over project links.
     
     When a sesman session is registered it's automatically linked with the lowest priority context (project, or directory if no project found). By default (configured with `sesman-1-to-1-links`) multiple sessions can be linked with a project or a directory, but only one session can be linked with a buffer. 
     
     Cider functionality (eval, completion, repl-switching etc) operate on linked sessions. When there are multiple linked sessions ambiguity is automatically resolved by the recency of the REPL buffers (configured with `sesman-disambiguate-by-relevance`). 
     
   - Show info on current links with `C-c C-s l`. Show info on current, linked or all sessions with `C-c C-s i`.
    
   - Micro-management of the server is not allowed (it's not useful and would complicate UI). All repls within a session share a server. Server can be either remote (`cider-connect`) or local (bootstraped within the emacs during `cider-jack-in-xyz`).
    
     In case of the local server, when the last connection is killed the server is automatically killed. `cider-restart` restarts the connection but not the server. `sesman-restart` restarts the server and all the connections.

At least two issues I still plan to tackle here:

   - Restart of SSH tunneled connection has not been tested and probably doesn't work 
   - REPL buffer naming system is no longer adequate. It should be possible to include session name as part of the buffer name and add more flexibility into the customization of buffer name templates.

----- 

A tot of no longer necessary or questionable functionality has been removed. The goal is to start from scratch and add only what is really necessary. I am listing all the removed functions for the ease of lookup through the github interface.

Removed:

    cider--connection-host,
    cider--connection-port,
    cider--connection-project-dir,
    cider--connection-properties,
    cider--connection-type,
    cider--guess-cljs-connection, 
    cider--has-warned-about-bad-repl-type, 
    cider--in-connection-buffer-p, 
    cider--quit-connection,
    cider--restart-connection,
    cider-assoc-buffer-with-connection,
    cider-assoc-project-with-connection, 
    cider-change-buffers-designation,
    cider-clear-buffer-local-connection, 
    cider-close-nrepl-session,
    cider-connections (variable), 
    cider-current-connection (variable), 
    cider-current-messages-buffer,
    cider-current-repl-buffer,
    cider-default-connection, 
    cider-extract-designation-from-current-repl-buffer,
    cider-find-connection-buffer-for-project-directory, 
    cider-find-reusable-repl-buffer,
    cider-make-connection-default,
    cider-map-connections, 
    cider-other-connection,
    cider-project-connections, 
    cider-project-connections-types,
    cider-prompt-for-project-on-connect,
    cider-read-connection,
    cider-repl-buffers,
    cider-replicate-connection,
    cider-request-dispatch, 
    cider-rotate-default-connection,
    cider-toggle-buffer-connection, 
    cider-toggle-request-dispatch, 
    nrepl-connection-buffer-name-template,
    nrepl-create-client-buffer-function,
    nrepl-post-client-callback
    nrepl-prompt-to-kill-server-buffer-on-quit,
    nrepl-use-this-as-repl-buffer,

   Connection Browser Functionality:
   
    cider--connection-browser-buffer-name,
    cider--connection-ewoc,
    cider--connection-pp,
    cider--connections-close-connection,
    cider--connections-goto-connection,
    cider--connections-make-default,
    cider--connections-refresh,
    cider--connections-refresh-buffer,
    cider--ewoc-apply-at-point,
    cider--setup-connection-browser,
    cider--update-connections-display,
    cider-client-name-repl-type,
    cider-connection-browser,
    cider-connections-buffer-mode,
    cider-connections-buffer-mode-map
    cider-connections-close-connection,
    cider-connections-goto-connection,
    cider-connections-make-default,
    cider-display-connected-message,
    cider-project-name,
   
Renamed: 

    cider-current-session -> cider-nrepl-eval-session
    cider-current-tooling-session -> cider-nrepl-tooling-session
    cider-display-connection-info -> cider-describe-current-connection
    cider-create-sibling-cljs-repl -> cider-connect-sibling-cljs
    nrepl-connection-buffer-name -> nrepl-repl-buffer-name
    cider--close-connection-buffer -> cider--close-connection  

    ## repl <> connection overlap cleanup
    cider-connections -> cider-repls
    cider-current-connection -> cider-current-repl
    cider-map-connections -> cider-map-repls
    cider-connection-type-for-buffer -> cider-repl-type-for-buffer
    cider-repl-set-type -> cider-set-repl-type

1 files changed, 1 insertions, 5 deletions

diff --git a/cider-scratch.el b/cider-scratch.el
index 2dded9fb..5838a6ef 100644
--- a/cider-scratch.el
+++ b/cider-scratch.el
@@ -44,11 +44,7 @@
       '("Clojure Interaction"
         (["Eval and print last sexp" #'cider-eval-print-last-sexp]
          "--"
-         ["Reset" #'cider-scratch-reset]
-         "--"
-         ["Set buffer connection" #'cider-assoc-buffer-with-connection]
-         ["Toggle buffer connection" #'cider-toggle-buffer-connection]
-         ["Reset buffer connection" #'cider-clear-buffer-local-connection])))
+         ["Reset" #'cider-scratch-reset])))
     map))
 
 (defconst cider-scratch-buffer-name "*cider-scratch*")