Support for LSP/tsserver Code Actions (#3437)

* Added tsserver and LSP code action support.
* tsserver refactors support added.
* Handling special case when new text is added after new line symbol.
* ale#code_action#ApplyChanges simplified.
* Initial attempt on LSP Code Actions.
* workspace/executeCommand added.
* Some null checks added.
* Add last column to LSP Code Action message.
* Pass diagnostics to LSP code action.

Previously ApplyChanges code was applied from top-to-bottom that required 
extra parameters to track progress and there was bug. I have changed code
to bottom-to-top approach as that does not require those extra parameters
and solved the bug.

Tested with typescript-language-server and it is working.

doc/ale.txt

@@ -3106,6 +3106,18 @@ ALERename                                                           *ALERename*
   in those files will not be updated.
 
 
+ALECodeAction                                                   *ALECodeAction*
+
+  Code Actions support for `tsserver`.
+
+  There are two different kind of actions supported for `tsserver`. If run in
+  normal mode then code fix will be attempted if there is error in that line.
+  If there are multiple code fixes available use will be shown input to choose
+  one. In visual mode `tsserver` will be queries for applicable refactors
+  (e.g. extract to constant or extract to function) and user will be given
+  choice to select the one he/she likes.
+
+
 ALERepeatSelection                                         *ALERepeatSelection*
 
   Repeat the last selection displayed in the preview window.