[ADD] new cases in API/WS doc

Needs a bit of review by @rco-odoo and @odony:

* alters the `write()` docstring to expand on writable values and try to expand/clarify the o2m/m2m protocol
* adds a convenience parameter to fields_get: when using it for user-read introspection, returning all attributes generated by fields_get is inconvenient. Adds a new ``attributes`` kw parameter which allows filtering the field attributes returned by fields_get.

Aside from that, 
* adds introspection, reports and workflows stuff to ws docs
* tries to make java examples slightly shorter by using static imports
* then makes them bigger again by making examples more self-contained (inlining of `domain`)