Addition of NSIDE, n-inc-angle, n-pol-angle to inspiral_extrinsics.py along with supplementing documentation

These changes add the above the variables to inspiral_extrinsics.py code. None of the calculations that are being done has changed. It only allows the user to specify the values for these variables and more control over the file. Temporary backwards compatibility is added.

This plot shows that the old and new file match exactly as well as the histogram.