Merge remaining sr1_knut_dev things, fix testswarnings

[JelleAalbers]

This merges the remaining commits from sr1_knut_dev into master. I could not resist a few slight changes to the formatting. @kdund could you have a brief look to check I didn't destroy anything accidentally?

This also fixes using non-tuples for indexing (deprecated in numpy) and a failing test for bestfit_minuit.

[JelleAalbers]

@kdund Any chance of having a look at this?

[JelleAalbers]

@kdund I would propose merging this, blueice will break for future numpy versions otherwise. Minuit support is likely already broken without this. Plus, your improvements deserve to make it into master :-)

I had a look through it, this will:

• Add support for the 'efficiency_name' source config option. This specifies the name of the parameter controlling the efficiency for that source. Sources not specifying efficiency_name are controlled by the likelihood-global 'efficiency' option (as before).
• Removes the deprecated LogLikelihood class, which already gave DeprecationWarnings for a long time. (One should use UnbinnedLogLikelihood)
• Allow weighting of the summed likelihoods in LogLikelihoodSum -- see its docstring
• Fix processing of minuit arguments (likely this worked only for old versions of minuit).
• Fix deprecated (in numpy 1.15, July 2018) use of non-tuples for indexing in pdf_morphers.

[kdund]

That'd be great-- I am unaccountably locked out of midway atm, once I am back I can confirm if it works on my side at least
(Setting a reminder)

[kdund]

Back on midway!
Yes, I'm happy to merge it now (is that my button to push?)