moved combine_ivm_maps; update '.update's
 * moved the combine_ivm_maps() function over from badpix.py to imarith.py
 * fixed the imhead.update instances that are now deprecated.
Added mkscaledtemplate.py and HSTFILTERS
 * new module mkscaledtemplate for combining template images
   of different filters and scaling them to match
   e.g.  F775W+F850LP ~ F814W
 * added the directory HSTFILTERS with HST filter transmission
   curves in support of the above
 * added a --templatefilters option to allow the above from
   the command line.
 * various other tweaks and bug fixes
 * tested minimally on MACS2129 parallel field GLASS data