Read and write a MultivariateGaussian prior to file

This MR allow the MultivariateGaussian prior type (!110 (merged)) to be read in and written to a prior file along with its associated MultivariateGaussianDist.

cc @colm.talbot @gregory.ashton @moritz.huebner

changed milestone to %0.5.2

approved this merge request

It looks like !501 (merged) caused some conflicts with this. Sorry about that.

Hopefully, it will actually simplify loading this prior class as you can define a from_repr method for the class.

changed milestone to %Future

@colm.talbot no problem. I'll try implementating this again using your new interface.

added 41 commits

• d635904c...3f25d4a7 - 40 commits from branch lscsoft:master
• 4838dd23 - Merge branch 'master' into read_mvn_prior_from_file

Compare with previous version

I've had a go at fixing this. Unfortunately, due to how the MultivariateGaussianDist and MultivariateGaussian prior work together it does not look like it'll be easily workable with the from_repr method. So, I've just had to essentially use the old method when this prior is used.

@colm.talbot @gregory.ashton @moritz.huebner would anyone be able to approve this commit? It seems to work fine and is something that I'll need for my cwinpy code.

approved this merge request

changed milestone to %0.5.3

approved this merge request

merged

mentioned in commit 0b1aa313