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
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