VIM-652 Add support for executing and mapping arbitrary IDEA actions

* no tests performed..! *

Example usage:
:nnoremap gi :action GotoImplementation<CR>
:nnoremap gu :action FindUsages<CR>
:nnoremap gcw :action RenameElement<CR>

Action overview:
https://github.com/JetBrains/intellij-community/blob/6c6cb47c5a41025549157d64643a98a89481260d/platform/platform-resources-en/src/messages/ActionsBundle.properties
Implemented :findaction
Fix action execution contexts, use a delay on popup actions to allow the command handler to unwind
Renamed :findaction => :actionlist + added statusbar error message when calling invalid action names
:actionlist added support for wildcards
ExecuteActionByName use the content context on actions with the EnabledInModalContext flag set

(cherry picked from commit d375740)
Fixed code style
Prettier output of :actionlist
Don't allow short names for IdeaVim-specific :action and :actionlist
Removed checks for action execution problems not reproducible at the moment

We need to collect more data from the beta testers about these problems.
Renamed ExecuteActionByNameHandler to ActionHandler

The name of an Ex command handler should correspond to the Ex command
name.
Merge branch 'action-command'
Added smartbomb to the list of contributors
VIM-652 Added a test for :action
Added `:action` and `:actionlist` to the docs
Updated dev version
Updated changes in plugin.xml
Links to GitHub and YouTrack in the plugin info