Add the database schema to the sqlalchemy docs

In order to show people that are reading the docs what the current
schema for the database is create a helper tool that upgrades the
schema to the newest version and then uses tabulate to create a
restructured text version of that schema which is then included in
the documentation.

Change-Id: Id215f88430971a4a083f9739fb2ec59d971dc8fa
Merge "Add the database schema to the sqlalchemy docs"