Plugins:
Moved plugins from BackgroundService to Device and adapted as needed
Plugins now implement their own broadcast receivers, instead of using a global one
Renamed ServiceLauncher to KdeConnectBroadcastReceiver
Implemented PluginFactory
Merged SmsNotifications and CallNotifications into TelephonyPlugin

Interface:
Started new GUI (uses ActionBar and other Android 4.0+ widgets)
Mpris and Plugin Settings activities are now per-device
Removed SettingsFragment in favor of SettingsActivity (for now)
Removed CompatClibpoard
Added a class to convert internal phone name to human-readable names.

Persistence:
BackgroundService now stores a list of know (paired) devices
Device now stores its name, trusted state and plugin list
Added setTrusted and trust/untrust logic to Device
The Settings activity now reads/writes the plugin settings from/to Device

(Sorry for this huge commit)