quant: scale psy-rdoq by lambda

Using L1 lambda in RDO is unorthodox, but we already do the same thing with
psy-rd energy and it seems to work decently well here weighting the
reconstructed DCT coeff against the RD cost in psy-rdoq.

The goal is for psy-rdoq 1 to be a safe and sane default
rdcost: add arbitray scale to make --psy-rd 0..2 range give acceptable quality
param: re-enable psy-rdoq range check for [0..10], print with two digits
quant: set lambdas at the same time quant QP is configured
analysis: nits
rest: improve documentation for psycho-visual options
slicetype: use fast intra scan unconditionally in lookahead

We don't want the lookahead output to be variable depending on --fast-intra
since this would make two-pass turbo mode more difficult.
param: enable --fast-intra for all fast modes and turbo first-pass, document