stereo_mpi: Minor comments
stereo_mpi: Add timeout for correlation option
dg_mosaic: Strings and array can be compared simply with ==
InterestPointMatching: Rm pseudo image copy
dg_mosaic.py: Closer to python 2.4
dg_mosaic.py: Make it work for python 2.4, 2.6, 2.7
Core: Added parallel interest point matching

This is not as fast it could be as I'm by default mutexing all
interaction with the camera model. (This is because of ISIS.)