Added script for suspending instances
Merge branch 'herja' of github.com:iPlantCollaborativeOpenSource/atmosphere into herja
BUGFIX - ATMO-431
Merge branch 'herja' of https://github.com/iPlantCollaborativeOpenSource/atmosphere into herja
Add support for request tracker
MachineRequest error fixed
Use django transactions and select_for_update to prevent race condition in instance_status_history.
	modified:   core/models/instance.py
Add suspend_instance from abyssinian-nightjar.
	modified:   scripts/suspend_instance.py
PEP8 Compliance. Add 'Enforcing' variable to settings, so that production can be tested
Merge branch 'herja' of https://github.com/iPlantCollaborativeOpenSource/atmosphere into herja
Catch system exit exceptions
Updated automated imaging tasks so that they run to completion, can be re-started at any point in time by running start_machine_imaging()
Merge herja+Abyssinian