Cleaned code and added comments
Added distance/azimuth/elevation computation in Location

- altitude field type has been changed to double (was float)
- added method to compute
	* distance over ground (2D) to a destination
	* true distance (3D) to a destination, using spherical or cartesian
coordinates 	
	* elevation and azimuth angles to a destination
- added a test class DistanceAzimuthElevationTest