VCS: Enable calling runVcs from non-GUI threads

* Introduce a proxy class for thread synchronization
* Use signals for appending text to output window

Change-Id: Iecbb010e6b6e9dab27d9862a43dafa450f2bb1f8
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>
VCS: Use runVcs for Command

* Removes duplication
* Supports all flags accepted by runVcs
* Supports output while running

Change-Id: Id067791760753184cd2516c23634564880ca5db0
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>
VCS: Introduce message style

Similar to compile and app output panes

Change-Id: Ib9ac6d8be880739ae78d0a39f7051cbe616e46c2
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>
Git: Show success message when command ends

Change-Id: I501c69df2a436d90270a6c2543c3e286bafef427
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>