All text editor actions were disabled. We want the actions to be enabled
when the focus is in the text editor widget in the Android manifest
editor.

For this the text editor action handler must differentiate between the
_editor_ and the _context_ that it handles. The one for the text based
manifest editor handles the manifest editor, but the context is specific
to the text editor part.

Change-Id: Ib91cc763cb27333a7d5b6e5b036dfead33961871
Reviewed-by: David Schulz <david.schulz@qt.io>