Parsing of detector lists

[tdixon97]

Currently this is a bit ugly.

• The user can give explicitly a list
• Or they can give an expression but it really has to be a single function giving a list.

We should support generic python expressions and probably also regex

[gipert]

Another thing that would be easier with a Python API

[gipert]

I vote for not implementing more features in the config file. For advanced usage, we should recommend iterating in a python script.