Rework contributing docs

Move folder to root of source to mirror nav (this breaks away from the
django folder structure).

I've ensured the docs are consistent in their use of "issue tracker"
(rather than bug/ticket tracker).
Clean releases nav entries

Remove boilerplate copy
Add a support section (based on getting_help.rst)
Add root nav nodes for upgrading and deploying
Move translation into contributing
Get left-hand nav right

Plus remove manual TOC in index - it will be reinstated later on.
Create new "getting started" section

Based on internals/getting_started.
Improve score calculation management command

Improve the logging and admin.
Include product score in Solr search index

So it can be used for boosting.