1.6.2-28.  Removed half-pixel offset in contour plots.

  This offset was introduced in 1.0.9 to workaround a bug
  (change #42 following the 1.0.8 release), but the
  workaround is apparently no longer needed.
Support background spectra stored in user-specified hdu
1.6.2-29:  cache_fun now supports caching of operator models.
Fix configure issues when building without heasoft
fix duplicate variable declaration in macro interface definition
Comment out heasoft nei functions no longer provided as of heasoft-6.16
regression test supports atomdb 2.0.2
1.6.2-30:  Update Changes.txt, increment patch level