Don't export jacobian

[dlfivefifty]

Conflicts with ForwardDiff.jacobian

[daanhb]

Yes good point. I've been thinking it might be better to put all of the maps-associated functionality in a separate submodule, and eventually in a separate package.

[dlfivefifty]

I would support that since it's orthogonal to domains

[daanhb]

Indeed. We identified a number of overlapping packages some time ago, but the majority of them don't support rectangular or other non-invertible maps so I went ahead and implemented what I needed to support e.g. parametric domains. But that should not be exposed when just using domains