Reorganize Diviner articles into user/ and tech/
Summary: Ref T988. I'm splitting the Phabricator documentation into two separate documentation books, one less technical and one more technical. Move all the .diviner article files around into src/docs/user/ or src/docs/tech/, accordingly. The only actual changes here are a couple of config changes in the .book files.
Test Plan: Regenerated user and technical documentation and saw stuff in the right places.
Reviewers: btrahan
Reviewed By: btrahan
CC: chad, aran
Maniphest Tasks: T988
Differential Revision: https://secure.phabricator.com/D6822