NEW: docproc: skeleton for lab2
ENH: docproc: completed background subtraction and high-contrast downscale
ENH: docproc: feature-complete with rotation
ENH: docproc: removed find_crosses (not used)
ENH: docproc: structured functions by three files
FIX: testdata: file extensions must be lowercase
FIX: forgot to delete file
ENH: ignore result files for testdata
ENH?: docproc: illustrate optangle with debug images