Project: datamanagement
Issue DM-4367: Fix bug and add unit tests for PsfShapeletApprox 
We discovered during this Sprint that this plugin was giving us faulty values for all the models except for SingleGaussian. I will fix that bug on this issue. Obviously, a better unit test would have caught this. I am adding a DoubleGaussian unit test, plus a test that the default models provide different results. Also a timing test for all the models, as we do not really have enough information about the performance of the shapelet approximation.
Story points: 3