Backend ability to create / delete instance images
Override the default instance launch image with cli option --image-name
CLI subcommands for creating and deleting images
Fix for resolving image name from config
Merge branch 'master' into capture_instance_images

Conflicts:
	gonzo/backends/__init__.py
	gonzo/scripts/instance/launch.py
Merge branch 'master' into capture_instance_images

Conflicts:
	gonzo/scripts/base.py
Fixed naming of image-delete function
Renamed cloud.nova_client to cloud._nova_client
standardized get_image_by_name errors
Better imaging function structure with standardized errors
Better script failures
Removed the unused CommandError and restructured image-delete
Removed now unused cloud.delete_image_by_name method
tests for image deletion laws
First draft of stack image-capturing and stack-termination.
Fix for aws image lookups
Renamed TooManyResultsError to MultipleResourcesError for consistency
Fixes for tests
Better docstring for Image._refresh and relabelled Image.running_state
Fixed stack running state reference (using constant instead)