Fixed point_source_id property arguments.
Fixed set_point_source_id function call.
Changed las.LASPoint_{Set,Get}PointSourceId.restype assignment to ctypes.c_uint16 so that it matches boost::unit16_t in src/point.cpp
Merge pull request #28 from rickhg12hs/master

Fixed point_source_id issues in python/liblas/{point.py,core.py}