This refactor has the intent of guiding a new OpenStack-Ansible
user towards his first contributions.
The deploy guide is now pointing towards the Developer Guide,
but there is was no guidance given, just a series of topics.
Here, the first page of the developer guide is an onboarding
page, explaining our repos, what's inside them, and how to
contribute. It then links towards all the sections, which
had to be restructured to match a wizard-style flow.
Change-Id: Ib2a5f2063c4dc58fc249ac94c3cd85bb281f28a5
3a4ca09d11