support for grayscale image I/O
support for grayscale image I/O

 * added ensure-list and ensure-vector

 * moved tiff-image class definition

 * gross cut-and-paste job for grayscale file I/O

 * fixed read-field-shorts when there was only one short to read (only
   return one short)

 * write-tiff-stream now calls write-tiff-grayscale-stream or
   write-tiff-rgb-stream as appropriate.

 * removed debug declarations

slyrus/retrospectiff