Isolated InstanceAction logic, removed from API

Highlights:
* Four new methods created for actions that require status updates in
  service/instance.py:
  * resume_instance(esh_driver, esh_instance,provider_id, identity_id, user)
  * suspend_instance(esh_driver, esh_instance,provider_id, identity_id, user)
  * start_instance(esh_driver, esh_instance,provider_id, identity_id, user)
  * stop_instance(esh_driver, esh_instance,provider_id, identity_id, user)

* New functions will:
  * Check quota (If necessary)
  * Run the driver-related functionality
  * Update status history (CORE)
	modified:   api/instance.py
	modified:   core/models/instance.py
	modified:   service/instance.py