search: move m_bestME[] from search to Mode structure
docs: improve --pmode documentation, the feature is fully functional
analysis: remove TODO comment, I've given up on the idea
api: allow --psy-rdoq values up to 50; it can be beneficial for film grain
encoder: give more warnings when features are automatically disabled

and add comments describing why the combinations are prevented.  Some of them
are simply impossible, the option would have no affect and so it is best not to
pretend it is enabled. Some will not be useful (have a negative impact on
performance with no compression improvement). And others are just currently
broken and not typically used.
Merge with stable
encoder: fix some obviously incorrect comments