No-detection mode interferes with '--partition-multithreshold=1'

[mkuemmel]

Looks like in 0.21 and the current develop requires partition-multithreshold switched off, and the default, which is on, leads to errors as discussed in #575 .

I consider this as a bug, and in no-detection mode this parameter should not be considered.

[marcschefer]

Yes, indeed multithresholding can only work if we have a detection image.

I think overall what we are missing is some kind of configuration validation system. We've had similar problems where we'd like to disable some combinations of options or print warnings.

The configuration system uses many configuration classes that are supposed to be modular and have the minimum of dependencies possible. Adding such rules to the current system is going to create a mess.

[mkuemmel]

Yep, I think we sometimes tried to solve this on a small scale with dependencies and then errors. I think the more options we have and the more new branches such as the no-detection mode we this gets more complicated.

At least we know now that there is a problem.