update preferences labels
ViewerGL: don't cast to int: use ceil() and floor(), and don't forget the last row/column
EffectInstance: only render once if tiles are not supported
Image: fix the last bug (!) in the optimized Bitmap::minimalNonMarkedRects()
both the effect and the output clip have to support tiles
update openfx
Merge branch 'workshop' of https://github.com/MrKepzie/Natron into workshop