trying to fix abstract method bug

trying to fix abstract method bug

trying to fix abstract method bug

Goonj error while playing track in background fixed

Download and cache support added

many bug fixed

made debug configuration same as release

Bug fixed ExoPlayerAnalyticalListenerImp suppressed for now since it …

…was causing fatal crashing on some build

addedAt, playedAt, completedAt converted to nullable Date, error fixed

addedAt, playedAt, completedAt converted to nullable Date