Play/pause and skip to previous/next song work. The currently playing song
name is shown on the Cor. The track length and progress are now shown as
we don't know how to send these yet.
- Rename MiBand2Service to HuamiService
- Move preferences around (Mi Band 2 has its own device specific settings now)
- Fix Cor menu items not syncing immediately in settings
- Try to support settings menu items on Mi Band 3 (buggy, disabled code for now)