data/eval/README: Add a recipe for manual tsvgs run
AnswerGSHook: Revamp the 'train from the only first correct answer' idea

The problem is that our model training is highly non-stationary now (new
trained model depends on the previous model - this is not desirable) and
it is a real problem both in terms of performance drift and
degeneration.

Therefore, do not do this in the initial phase, making phase 1 the first
natural 'pruning' phrase from the angle of both reduce-to-100 and this,
and in the followup phases use the score from the previous phase for
correct answer selection. This keeps the nifty feature but makes the
model stationary again.
AnswerScoreLogistic: Update the model