[IMP] doc: indexify index

* opt-in toc navification
* unhide index toctree, it's now back to a list of documents
* remove text thing
[IMP] doc: more indexy index
[IMP] doc: move old API sections to orm toplevel

also move porting checklist/doc/thing to bottom of document, it's mostly
for seasoned or internal developers
[IMP] doc: try to make some bits of the porting guide less confusing
[FIX] tests: make self.assertRaises() return the expected object
[IMP] doc: rename WS page, lift to top-level
[IMP] doc: wording of method-calling introduction
[IMP] doc: have ws page take whole page width

Doc pages used container() which is width-limited, works acceptably for
single-column content but WS page takes 2 columns with code, having as
much space as possible is a much better idea.

Mayhaps it should even use lg-column(2) instead of md-column(3)?
[IMP] doc: improve index, WS page
Merge branch '8.0' of https://github.com/odoo/odoo into 8.0-linux64