JVET_P0243 / P0244 / P0429 : SPS HLS Cleanup

 - Signal a single bit depth to be used for both luma and chroma.
 - Use u(4) for SPS IDs in the SPS syntax as well as in other places for referring to SPS.
 - Code chroma_format_idc with u(2).
 - Code log2_max_pic_order_cnt_lsb_minus4 with u(4).
 - Specify the value range of min_qp_prime_ts_minus4 to be 0 to 48, inclusive.
 - Specify the value range of log2_min_luma_coding_block_size_minus2 to be 0 to log2_ctu_size_minus5 + 3, inclusive.