analysis: RDO based BIDIR decisions

At RD 0, 1, and 2, this changes 2Nx2N bidir from a SATD decision to an SA8D
decision.

At RD 3 and 4, if the bidir SA8D cost is within 17/16 of the best inter cost,
then it makes an RDO decision between bestInter and Bidir (allowing psy-rd to
influence the decision, which is the whole point)

At RD 5 and 6, 2Nx2N BIDIR is yet another RD choice at the same level as 2Nx2N
inter and rect and amp. (psy) RDO picks the best mode for each block.
rdcost: experimental slice-type based psy-rd scale factor
param: remove --b-intra from --tune grain, document rdoq restriction
param: raise --nr limit to 2000
noiseReduction: apply only for I and P, move NoiseReduction to quant.h

This doubles the number of quant nr categories; intra blocks now use the lower
half.
quant: allow --nr in all slice types evenly
Merge
analysis: fix bidir non-determinism in --pmode --rd 5