First Commit

This is the 1st commit for the blib library. This contains a few
cross-check files, as well as the parent library.
Added gaufit.py, psf-slice.py and blib.py

gaufit.py fits two Gaussians to a profile.
psf-slice.py performance a slice of a 2D image, usually a psf image.
blib.py is the new library for all these helper functions.
Expanded blib.py, reduced psf-slice.py

All the generic libraries have been moved from psf-slice.py into blib.py
Updated blib.py, psf-sice and added psf-fit-overlays.py

psf-fit-overlays.py simply overlays psf-cross-sections from two image
files - the main psf image and the fitted model.