Gerrit: Some more cleanup

* Remove qualification for types in Gerrit::Internal
* Remove action/command pair. Action is stored in Command.

Change-Id: I946bedd3909e217279e9d7a538e8460e0a61de0f
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>