Fix several issues concerning NestingBricks and ActionMode
Remove call to saveProject in addNewBrick

saveProject should not be called whenever a brick is added. Every new brick added
would cause the project to be saved which would take some thime if the project
already has many objects.
Merge pull request #768 from Catrobat/ForceCloseWhenCopyingForeverLoopsFromActionMode

Fix several issues concerning NestingBricks and ActionMode
Fix #759