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