Post 6.7.1 fixes

[brown170]

A collection of changes that may already be in a development branch, but here are the fixes identified by Dave

[mattooca]

I think all of these fixes have either been included in master or fixed another way. For example we're now using raw strings for most docstrings instead of double-escaping LaTeX stuff.

The main functional difference with master is the covariance file naming convention in brownies/bin/endf2gnds.py: gnds-covar.xml (master) vs. gndsCov.xml (this branch). I prefer not to change that convention. If scripts need to load covariance data, the best option is to use ReactionSuite.loadCovariances()

[mattooca]

I'd like to close this MR unless you object.