Gsl optimizer solver types

Adds all the available GSL multidimensional optimization solver types. I know that perhaps the *2 algorithms may be redundant, but GSL kept them older ones around, so I feel like we should as well (at least, in the absence of going in and looking at all the details).

Untested so far. Need to create unit tests to hit all these things.

@dmcdougall please make sure I didn't muck up the rebase.
You can delete this `\todo` now, it's been done :)