- move api as "reference" guide and reword as Python client;
- consolidate shell and cli as part of the "CLI" guide;
- remove the "how_to_participate" page and use part of
the content from the old index for a minimal "contributor"
guide which redirect to the sahara contributor guide
(no need to duplicate the information);
- remove few references to doc/source/api from tox.ini and
.gitignore (for some reason the directory was cleaned).
Change-Id: Iff049ab32a7695a7a58bd370a1517b1ed7d2f048
889cbb5613