PLCgen self-certification test set: make it easier to compare TIA Portal output against expected test output

See discussion at #1019 (comment 2838629).

The idea is to make a script that can compare the output of TIA Portal automatically against the expected test output. It should handle the different possible representations of enums, possibly differently rounded reals, variables that can be in a different order, etc.

Addresses #679, #798 (closed)