Add a 4 Gaussian Model

[HKaras]

A user (Joerg Reichenwallner) has requested that a default 4 gaussian distance model is created.

This time I have another subject of interest. We are seeing a consistent set of 4 distances in our 4pDEER data and I was wondering if DeerLab is capable to tackle that.
So far, I "only" saw a 3 gaussian routine that could be readily used. Is there anything implemented yet in DeerLab which would suffice to handle that 4-distance peak problem?

Maybe we could even expand this to have a generalised n-gaussian model?

[stestoll]

Gaussian mixture models with more than 3 components tend to be very difficult to fit, since there are too many parameters. The result is often complete overfitting with uninterpretable results. The only situation where they might work is in the case of a multi-datasetfit, where individual traces isolate 2 of the Gaussian, for example in a titration dataset.