Fix bug where station is forgotten when using physical power button
Remove revert() as not used anywhere
Explicitly check if device is online when returning initial state
Service shouldn't be manually changed to null
Throw if changing to service that does not exist
Test that services manager track changes in settings

- make settings emit 'update' events
- return 'ready' promise on initial fetch of settings
Default station should be radio1 since it's first in the list
ServiceManager provides initial default station to play action
Merge pull request #9 from radiodan/fix-station-being-forgotton

Fix bug where station is forgotten when using physical power button