Add test for minimizers and confirm that DFO is working

[andped10]

Add test for minimizer LM and base

When working on EasyReflectometry I was not able to get the DFO minimizer to work and it seems to be a problem with EasyScience. We should add tests for each of the minimizers in EasyScience. Currently we only test the factory and Fitter but not the different minimizers.

[damskii9992]

It turns out we do not even test the Fitter correctly, as all the minimizers are currently broken. The PR should however fix this bug.