Want BAYERPAT FITS/XISF headers

[Dale Ghent]

When PI and other apps debayer an image, they look at the BAYERPAT FITS headers for hints on what the image's bayer pattern is (RGGB, BGGR, GBRG, etc). PI requires this for Auto mode, otherwise one has to manually specify the correct mask to use in the Debayer tool.

However not all applications use a standard notation for these fields. PI will grok RGGB, but AstroArt will only understand GBRG. There is some backstory in this thread over on the SharpCap forums: https://forums.sharpcap.co.uk/viewtopic.php?t=1098

[Dale Ghent]

BAYERPATT should exist with BAYEROFFX and BAYEROFFY. The COLORTYP keyword is largely not used and certainly not by PI