WIP: Try wrapping section content in html classes

[jnothman]

Trying to make sections stylable (i.e. putting them in HTML elements with specified classes, like numpydoc-section and numpydoc-{parameters,attributes,...}) turns out to be quite hard:

• wrapping section headings breaks parsing of field lists, so we focus on section content (even though tooltips and link anchors on section headings would be really useful IMO)
• using .. rst-class:: works sometimes, but labels every paragraph in an unstructured section, and does not wrap autosummary tables
• wrapping in .. container:: (the right way to do it) adds the class container to the HTML div (this is hard-wired into docutils), which interacts with bootstrap.css
• wrapping in .. raw:: html \n\n <div class="...."> sometimes works, sometimes doesn't. It seems that docutils sometimes closes the opened <div> automatically before the following content (this happens for definition lists, but not for an autosummary table). Looks like a bug, but I've not yet understood where it's coming from.
• there might be a doctree-level solution, but I imagine in some cases it would involve a container node, raising the same issue as above.

This PR uses rst-class to add a class to parameter listings, as a proof of concept. Better would be to use .. container:: or equivalent (I've tried creating my own directive, but copying the existing container class doesn't help because all the writing logic is hardwired in docutils), but we need to work out a way to disable default .container styling from bootstrap, which in scipy central's theme sets width: 80%.

I thought this would be more straightforward. I'm not convinced anything in reST is straightforward.

Related: #88

[larsoner]

wrapping in .. container:: (the right way to do it) adds the class container to the HTML div (this is hard-wired into docutils), which interacts with bootstrap.css

I wonder if those of us who use sphinx-bootstrap-theme should heed this advice:

https://sourceforge.net/p/docutils/bugs/267/#6d70

In particular, we could build into sphinx-bootstrap-theme CSS the necessary overrides to undo the docutils.container "damage" to the Boostrap container class.

Then this PR would be much simpler, right?

[larsoner]

... oh wait, the problem is that we would have to undo all bootstrap-related stuff to make the "container" class that gets added be a no-op in this situation. Never mind :(