Write down steps how to debug heuristics

[hlibbabii]

It might happen that the proposed heuristics yield worse metrics even though they seem to be reasonable. We need to have a list of steps that can be done to understand what's wrong, e.g.:

• Check individual datapoints on which metrics degrade;
• Check how weights of the data model changed;
  etc.

[hlibbabii]

first draft is here: https://giganticode.github.io/bohr/DebuggingHeuristics.html