The issue was that KoColorSpace::bitBlt() only accepted composite ops from
its own color space, while at the same time allowing KoAlphaColorSpace to
blit in a differing source color space and substituting the composite op
accordingly, specifically to allow painting.

Since we cannot acquire most composite ops from KoAlphaColorSpace, some
restructuring was necessary:

- KoColorSpace::compositeOp() and ::hasCompositeOp() now take an optional
  destination color space to acquire the desired composite op
- KoColorSpace::bitBlt() accepts composite ops from source color space
  if it's going to work in source color space; this also avoids the lookup
  for substitution on each call
- KisPainter delays fetching the composite op until the source color space
  is known and caches the result
- change KisPainter::compositeOp() to compositeOpId() since we can no
  longer return an actual composite op
- since recompile time can't get any worse, take care of th...