Update database partitions with review changes

[lbboe]

Overview

This is documentation for the new partitioned databases feature. It covers the new APIs as well as provides a guide on actually using the feature.

Related Pull Requests

Main feature PR: apache/couchdb#1789

Checklist

Documentation is written and is accurate;
make check passes with no errors

[wohali]

Hi @lbboe ! Thanks for this work. I won't be able to take a look until next week at the earliest.

I didn't get to congratulate you for your first contribution to CouchDB in the last PR, so let me do so now - WELCOME! 🎺 🐻 🍇

We'd love to have you join our developer community, which is over on our mailing list: dev@couchdb.apache.org. Here's our direct links to join any of our lists: http://couchdb.apache.org/#mailing-lists

[lbboe]

Thank you, wohali. I'll check out the mailing lists.

[kocolosk]

Since this is targeting @davisp's other Pull Request as the base branch I think a quick 👍 from him should be sufficient to include it into the more complete review there. Paul, what do you think?

[davisp]

+1