Merge pull request #1 from EmilWestergren/master

Added code for YUV420Semiplanar
Cleanup.
Added RasterYuv420Semiplanar.
Merge branch 'master' of https://github.com/cogneco/ooc-draw

Conflicts:
	test/ImageFileTest.ooc
Fixed bug when converting from RasterBgr.
Added a test for converting from Bgr to Yuv420 and back again.
Added file open function in RasterImage for unknown types
Merge https://github.com/cogneco/ooc-draw