Add ppImage recipe value APPLY.BURNTOOL defaults to TRUE.
If USE.DEBURNED.IMAGE is set burntool will be applied in ppImage
if APPLY.BURNTOOL is true. If APPLY.BURNTOOL is false burntool will
be applied using the burntool program by chip_imfile.pl. If USE.DEBURNED.IMAGE
is false (default for other cameras) burntool will not be applied at all.
Also added recipe CHIP_PRESERVE_BG_AUXMASK which will be used for M31
processing. CHIP_PRESERVE_BG changed to set MASK.AUXMASK false
Added M31_BG_PRESERVE reduction