Remove unused channel

- Be more flexible around device's metadata (match amon schema)
- Don't send through all device when editing, only the edited keys
- Be more careful around posting property_data (don't post it when it's
  not edited)
Merge pull request #528 from MastodonC/feature/null-chan-fix

Remove unused channel
SPAAAAAACE
WIP
entity data can now handle attached profiles
MOAR tests
WIP
Test exists?
WIP
Update test
Better checking of whether profiles exist.
Add or match uuids.
WIP
WIP
WIP
Improved validation