Improve documentation of APIs
Improve documentation of APIs

* Sphinx crashes with a recursion error when trying to document Models
fields. Remove the fields from the documentation altogether, they didn't
bring much value anyway
* Gone through all the API pages and removed many useless autodoc with a
mix of __all__, :exclude-members: or by defining more precisely what we
want with :autoclass:, :autoatttribute:, ... or simply removing them
* Changed the order of a few autodocs by putting the most useful
classes/functions first
* Improved a few docstrings

OCA/connector,OCA/connector