NAME:
  blurmap
 PURPOSE:   (one line only)
  Apply spherical blurring to a map
 DESCRIPTION:
 CATEGORY:
  Numerical
 CALLING SEQUENCE:
  blurmap,inmap,blurradius,outmap
 INPUTS:
  inmap - Rectangular array which contains a map of a spherical body.  The
            coordinate scheme used is documented in RENDER.PRO
  blurradius - radius of the blurring function in degrees (<90)
                 a gaussian filter is used and this is the FWHM of the filter
 OPTIONAL INPUT PARAMETERS:
 KEYWORD INPUT PARAMETERS:
  OUTSIZE - two element vector that gives the size of the output map.
              Default is the same as the input map.
  MAPID   - String that identifies the map this is computed for.  The default
              value is 'default'.  This is used to control the cached values.
              If the MAPID changes, the internal values are recomputed.
              Also, if the blurradius, inmap size, or outmap size changes
              the cached is recomputed.
  RESET   - Flag, if set, forces a cache refresh
 OUTPUTS:
  outmap - Output map smoothed to desired level
 KEYWORD OUTPUT PARAMETERS:
 COMMON BLOCKS:
 SIDE EFFECTS:
 RESTRICTIONS:
 PROCEDURE:
 MODIFICATION HISTORY:
  Written by Marc W. Buie, Lowell Observatory, 2003/09/18
  2015/07/01, MWB, added caching and MAPID/RESET keywords