Generalize non standard heuristics

[joxeankoret]

Some heuristics aren't in the file diaphora_heuristics.py because they contain some logic that cannot be trivially/easily ported to the logic of having a long list of dictionaries with SQL queries. Write a new mechanism to accommodate most/all such heuristics.

PS: I'm excluding those heuristics that are purely procedural and aren't exactly a set of SQL queries.