testing whether RTD will now build with latest ZEO

I hate forking.

Support more db parameters

pool_timeout, cache_size_bytes, historical_pool_size,
historical_cache_size, historical_cache_size_bytes,
historical_timeout, and large_record_size

comment out latex_logo to get RTD to build

Change to using package pylons-sphinx-themes and remove git submodule

Add pylons-sphinx-themes to tox deps. Probably not the best way to do it, per https://github.com/Pylons/pylons-sphinx-themes#update-toxini

- Note that RTD has not been building. For some reason, RTD tries to install an alpha version of ZEO. See https://readthedocs.org/projects/zodburi/builds/4246953/

Add missing ClientStorage constructor kw args to resolver.

Fix link to documentation

Those releases are what we import, and have final Py3k-compatible releases.