keep max TU in #define for possibility of keeping the parameter

TU max/min size are constants in the VVC draft. Reflecting this in the software.

Speed-Up for ISP when JVET_M0464_UNI_MTS is enabled. It can be enabled/disabled with the config. file parameter ISPFast.

When enabled,
-it merges all full RD intra mode lists into one,
-it tests fewer non-DCT-II transforms if ISP is likely to become the best mode and
-it stops testing intra modes for an ISP split if all sub-partitions obtained a zero-cbf.

Results in CTC:

AI -> 0.04% loss, EncT = 97%, DecT = 100%
RA -> 0.01% loss, EncT = 99%, DecT = 100%

Clean-up of 2 parts in the ISP code that are redundant. The changes do not alter the performance in any way, i.e., the results are exactly the same.

1) In the full RD intra mode tests loop (estIntraPredLumaQT) there is the following condition:
    if ( uiOrgMode <= DC_IDX ) -> do X; else-> do X.
Since X is the same in both cases, the redundant code has been removed.

2) In xRecurIntraCodingLumaQT there is the threshold definition

double threshold = nSubPartitions == 2 ? 0.95 : subTuCounter == 0 ? 0.67 : subTuCounter == 1 ? 0.83 : 0.91;

Since subTuCounter can never be 0 (it is at least 1) at the time this expression is evaluated, the code has been simplified in the following way:

double threshold = nSubPartitions == 2 ? 0.95 : subTuCounter == 1 ? 0.83 : 0.91;

- all elements of SPSNext are moved into SPS
- syntax elements of SPS are sorted according to draft (as far as possible)
- comments were added where software and draft diverge

Remove unused contexts and split intra mode contexts into luma and
chroma sets to align with text description

There is a conflict with JVET_M0427_INLOOP_RESHAPER that is triggering a debug assertion that checks that the width is not 1.

- remove alternative code path for HM_EMT_NSST_AS_IN_JEM
- remove code in DMVR_JVET_LOW_LATENCY_K0217 (was not defined)

switched default value for CodingStructure::initStructData::QP from -1 to MAX_INT (signalling that the QP value for the CS should not be set)