JVET-R0068: Aspect 1 - slice_type constraint and Aspect 6 - signalling of conformance window parameters

JVET-R0068: Aspect 1 - Specify that sh_slice_type shall be equal to 2 (intra slice) when the NAL unit type is an IRAP NAL unit type and the current picture is the first picture in the current AU. JVET-R0068: Aspect 6 - Require the value of pps_conformance_window_flag to be equal to 0 when the picture width and height are the maximum picture width and height, and infer the values of the PPS conformance window syntax elements to be the same as those signalled in the SPS if the picture width and height are the maximum picture width and height and to be equal to 0 otherwise.