Add possibility for regex checker with regex from cmdline or config file

[bavovanachte]

[bavovanachte]

The use case:

MSDEs are including CI in their workflow. They would like to check the warnings coming from the simulation.

Main issue is that the warnings they want to check are not generic. (like ncelab: *E). So it doesn't really make sense to add a builtin checker for this.

[bavovanachte]

Thoughts @Letme @SteinHeselmans ?

[Letme]

This will open whole new can of worms, but I think we can allow it. Flexibility by existing structure should be there. We will loose possible contributions for more generic checkers (like compilers) which might also benefit other users - and where other users can improve the checker regex as well.