vslsmas: Support more YUV420/YUV422/YUV444 planar formats for output.
vslsmas: Fix background black maker.
vslsmas: Add 'format' option.

This option forces output pixel format defined in VapourSynth.
This option is available if 'variable' is false.
Currently, the following formats are supported.
	YUV420P8
	YUV422P8
	YUV444P8
	YUV420P9
	YUV422P9
	YUV444P9
	YUV420P10
	YUV422P10
	YUV444P10
	YUV420P16
	YUV422P16
	YUV444P16
vslsmas: Add _FieldBased property for each video frame.
vslsmas: Add YUV410P8, YUV411P8 and YUV440P8 output format.