Updates PGLowLatencyAudio to Phonegap/Cordova > 2.1.x

* Replaces deprecated org.apache.cordova.Plugin API with org.apache.cordova.CordovaPlugin
* Adjusts default value for the number of voices to 1 instead of 0
* This also seems to fix problems I had with the plugin where the sounds were mixed up (all sounds where there, but the wrong sounds were played consequently, i.e. sound2 was played although sound1 should be played)