JVET-S0096 aspect 1: a RPL constraint

The request is for JVET-S0096 aspect 1, a constraint is added in decoder side; JVET-S0096 aspect 3 is a spec. bug fix for rpl_idx[i] inference rule, software is correct, no need to change software; JVET-S0096 aspect 4 is a spec. bug fix for collocated picture check, software is correct, no need to change software; Moreover, JVET-S0095 aspect 5 is a semantics bug fix, no need to change software; JVET-S0095 aspect 6 is a change in inference condition for sesibility, no need to change software.