Fixed sky location functionality, and bug fix for extrinsic parameter proposal

Bring the sky fix branch up to date, and this also fixed the issue with the Psi proposals. Note that there's still something weird going on with the Phi (external parameter) prior recovery when using the orientation proposal, so someone should look into that (this is a bug unrelated to the sky fix stuff)

Usage for fixing the sky location is in the --help output, and is:

  --fixRA                  right ascension in radians of fixed sky location
  --fixDEC                 declination in radians of fixed sky location

if --fixSky is set without --fixRA or --fixDEC then it defaults to ra and dec of 0.