The actions are already lazily instantiated in
TextEditorActionHandler::setupActions(), so there should be no need to
call initializeActions() in all plugins on startup. Only the main text
editor plugin will still initialize its actions, to make sure the menu
items are there.

Moved unCommentSelection() in creator/libs/util so we can use it for other C-like languages (e.g QML and JS).

Improved the DuiDocument and keep a working copy of the document in the editor, also use the QML api.