* The document is no longer only for developers, so the title of
the top page is updated.
* In the current document standard, docs for contributors are
placed under contributor/.
* Title levels are rearranged to be shown appropriately
with openstackdocsthems.
* Fixes many sphinx code-block for better rendering.
Change-Id: I36fc80d1c1e5382597099b86df3bbf009ce06902
27b2222a3d