use nv.TopologyOrWeightMutator
use CHECKERLUTION_SCAPE logging tag
add expvar support and call checkerlution.RunPopulationTrainer
use uuid in cortex id
lookupFitnessHistory and TestLookupFitnessHistory
realized that recording the reverse direction score is not fair and gives unfair advantage to "trivial wins"
tweaking parameters a bit .. higher fitness threshold, smaller population