Mercurial: Disable hidden menu entries

To avoid shortcut ambiguity

Task-number: QTCREATORBUG-13364
Change-Id: Ibce1701be72376845624856b5de097332aaaccae
Reviewed-by: Tobias Hunger <tobias.hunger@theqtcompany.com>
Git: Disable all actions when inactive

Except "Create Repository"

Change-Id: Ie012c3af349e0706e95b1cf09466a4f23c82c4d0
Reviewed-by: Tobias Hunger <tobias.hunger@theqtcompany.com>
Perforce: Cleanup all actions enable/disabling

Change-Id: I0da22e5ddc18f0cb11f44bdaf6aafbe83907bee3
Reviewed-by: Tobias Hunger <tobias.hunger@theqtcompany.com>