Optimizer

Ok, optimizer is ready. I'm still documenting the code perhaps, but I'd somewhat rather do that from mainline so that others can review and suggest things.

This merge will not affect GWINC core, although maybe review main.py to make sure I didn't screw something up when I refactored the FOM argparsing into a function (reuse!)

To show what that this can do, I made some documentation and a tutorial in the docs folder. I have also added the doc compilation to the CI config. You can see it at

https://lee-mcculler.docs.ligo.org/pygwinc/optimizer/overview.html