EditorManager: adding save (as/all) to editor list's context menu

It is confusing that save is missing in the context menu
of the editor manager.

Split mode requires to use different actions then the ones
in the File menu, since the editor in question might not be the
current editor.

Change-Id: I47cd5295f7a3b58906e9b158e88d9128142d4311
Reviewed-by: Alessandro Portale <alessandro.portale@digia.com>