mostly work on correlation functions
- new correlation rotation function added
  - This is the 3rd generation and is called
    rotate_correlations_new until the commit
    in which the older two generations of this
    function will be removed and this one renamed
    to rotate_correlations.
  - Found bad bug in rotate_correlations_old which
    is what has been generally used until now.  This
    affects the data for the TT component and all TT
    data previously computed should be recalculated!
  - The newest function is recommended as it is the
    first to handle horiz. auto correlation sets.
- added horz_correlations_sets which is highly
  useful for handling horizontal correlations
- added a few more xc functions, lots of fixes and
  changes for ease-of-use were also added to existing
  xc functions (too many to list here)
- dropped some debugging lines from ttalign
- several minor documentation updates