Moved V8 util function to V8Utils.
First draft for setting the music delivery callback and retrieving a buffer with the audio data.
Further work in progress on issue-52.
This commit provides (mainly):
* useNativeAudio and useNodejsAudio
* compile flag --native_sound=true|false
Moved ownership of Player and AudioHandler to the application / NodePlayer instead of singleton and Spotify.

Implemented NodeJS audio with a timer instead of asynchronuous callbacks.
Some cleanups
Merge branch 'issue-52' into development

Conflicts:
	src/callbacks/SessionCallbacks.cc
Renamed native_sound to native_audio for consistency. Default value is now true so the basic npm install is as before.