lengthUVLC() is still duplicated in scaling list and ALF code

Picture Header data are not valid for reference pictures as they are
overwritten when parsing each picture header.

Configuration: removed interdependencies between chroma QP config parameters. Warning: not backward compatible. MaxCuChromaQpOffsetSubdiv <0 is no more used to disable the feature. Empty QP offset lists play this role. To enable the feature, now you have to specify chroma QP offset lists.