Expose "applyrefact:applyAll" as a hie command

[alanz]

Register this on startup as part of the capability negotiation, so it is available in all clients.

This obviates the need for haskell/vscode-haskell#168

[fendor]

Is it also possible to include other commands? Such as ghc-mod:Insert Type which will no longer work as soon as #1126 lands?

[alanz]

@fendor I am proposing only to add a command callback for an existing function, exposed as a code action, not to change the implementation or existence of the function in hie.

Something like the todoCmd exposed in the example2 module.

haskell-ide-engine/src/Haskell/Ide/Engine/Plugin/Example2.hs

Lines 99 to 107 in c253cbb

	codeActionProvider :: CodeActionProvider
	codeActionProvider plId docId r _context = do
	cmd <- mkLspCommand plId "todo" title (Just cmdParams)
	return $ IdeResultOk [codeAction cmd]
	where
	codeAction :: J.Command -> J.CodeAction
	codeAction cmd = J.CodeAction title (Just J.CodeActionQuickFix) (Just (J.List [])) Nothing (Just cmd)
	title = "Add TODO marker"
	cmdParams = [toJSON (TodoParams (docId ^. J.uri) r )]