Move cartridges into Mongo

* Cleans up group_override flow throughout the code 
* Move storage of downloaded cart info to the component_instance 
* Persist gear size and addtl_fs_gb storage on the group instance 
* When adding a cartridge, track the ID of the cart all the way through 
* Allow all application options to be passed to create on REST API 
* Allow all relevant cart settings to be passed to cart add on REST API 
* Support cartridge upgrade (simple) via update_requirements 
* Implement 'migrate' and 'clean' in oo-admin-ctl-cartridge
* Allow domain to be created on app create via REST API
* Remove Profile from the cartridge model 
* Disallow creating cartridges with more than one component 
* Add many more unit tests for app and cartridge logic

Implements origin_broker_193