Git: Replace findRepository with VcsManager::findTopLevel

Take advantage of its cache

Change-Id: Ibf3b3b59821a92cd4475c6f8d6dd8212983d5c96
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>
Debugger: Maintain slider position in watch view

Setting column width seems to reset slider positions, needlessly.
Work around.

Change-Id: Ifa6c6a204dd2fbd7ad3dada0c386b697ae7a4100
Reviewed-by: Christian Stenger <christian.stenger@digia.com>