Ability to create task groups without objects
Updated frontend error checking
Change to task group object task model
Fix email notifications for tasks without objects

I didn't really improve the code with this :(
Whitespace fixes
Updated down revision
Fix status propagation for cycle_task_group_object
Fix an issue with Workflow cloning
Merge branch 'develop' into feature/task-groups-without-objects

Conflicts:
	src/ggrc_workflows/__init__.py
Merge pull request #1826 from reciprocity/feature/task-groups-without-objects

Ability to create task groups without objects