This adds a call in sphinx to automatically generate the dashboard
description pages. It's a little bit of a hack, but works with "tox
-e docs" and the readthedocs build. This means we don't have to have
an external job running a separate build of the dashboard overview
page.
A couple of other things to integrate this and make the docs more
usable; we use the readme as the main page, fix up the links, use
sections in the template and add a clickable link to the dashboard in
each overview page.
I'ved tested this with readthedocs which you can see at [1]
[1] http://gerrit-dash-creator-dashboards.readthedocs.org/en/latest/
Change-Id: I027a21a40a0e35817b8a29996a48393743b282b0