Commented out pthread_barrier code.

pthread_barrier_t isn't supported in iOS
Restructured addAudioObject callstack

Sonic now has 5 public methods for adding an AudioObject:
(1) With just a filename (location defaults to the origin, velocity defaults to zero)
(2) With a filename and a location (velocity defaults to zero)
(3) With a filename and a location in polar coordinates (velocity defaults to zero)
(4) With a filename, a location, and a velocity
(5) With a filename, a location in polar coordinates, and a velocity

These in turn call one of three World::addAudioObject methods:
(1) Filename
(2) Filename and location
(3) Filename and velocity

Polar coordinates are converted to cartesian coordinates when appropriate before being passed to one of these three.
Each of these three methods corresponds to a similar AudioObject constructor.

Note that for an object to have a specified velocity, it must have a specified location.
added sonar sound
finished restructuring, but with linker errors
now use iOSSonic, but no playback
onCallback now working