Added life-cycle sounds for debugging.  Turn them on by sending debug: true to configure method.  also must enable background-audio background-mode manually in XCode.  See defines at top of CDVBackgroundGeoLocation.m for the sound-definitions.

Important to check for existing bgTask and abort, otherwise we're left with outstanding unkilled bg-tasks, resulting in ios killing the app and filing a crash-report

Uhoh, having app crashes when we try to modify current CLLocationManager settings by stopping/starting.  setConfig merely sets instance vars.  settings take effect only after the natural progression of Location events

Discovering that aggressive tracking cannot be initiated from a background push.  when started, ensure we always set isMoving: false

Introduce setter-methods for distanceFilter, stationaryRadius.  ignore calls to updateCurrentLocation when there already exists a bgTask