Added Uv color format
Added Raster UV class for use with RasterYuv420Semiplanar
Added middle abstract class for semiplanar YUV formats (following the same structure as for planar YUV)
Renamed file/class
Added class for YUV420 semiplanar format
Added test case for YUV420Semiplanar
Updated use file
Merge pull request #1 from EmilWestergren/master

Added code for YUV420Semiplanar