Neaten Application definition

Fixed singleton instance initialisation
Removed client secret from API initialisation - not required unless performing authorization.
Add rxjava dependencies to pom

Also updated Anroid to 4.3_r2
Neatened dependency definitions
Rename WallpaperSettings
Use Square Retrofit for API communication
Add JSON format to all request query strings
Remove .json suffix from API endpoints

This is now set via the ScRequestInterceptor
Use IOC in ImageDrawer
Remove unused API endpoints
Add compile time debug switch to WaveformProcessor
Minor cleanup

Make Track id a long, not String (as per API definition).
Allow configurable duration for ImageScheduler.
Some class and method renaming.