[ADD] website: added support for invoking a server action through controller

website: added website/action/<id_or_xml_id> route, that runs the server action designed
by its id or xml_id. Only code server action returning a template give a result. The
template is displayed. Other or not existing server actions redirect to the homepage.

website: added an override of ir_actions_server: evaluation context gets request for
evaluation, to enable request.render(template_name); also returns template the same
way action is returned for code server action;
[IMP] website: ir_actions_server: only published server action can be invoked from the front-end
[IMP] website: removed dummy data used for testing, added a first
demo template + server action callable through the front-end, working
on partners. Some king of simple partner directory.
[IMP] website: server action in front-end: updated demo data
to show something vaguely complex that 'everyone' can do using 2 server actions
and 2 templates: a basic partner directory.
[FIX] website: server action demo data: ValueError is not defined, do something generic
[MERGE] Sync with trunk
[ADD] website: added forgottent view file for ir_actions
[IMP] website: server action controller: no need to add post, everything is on request
[IMP] website: server action: response is a better keyworkd than template
[IMP] website: server action in front-end: improved demo data, a mini posting mechanism
[DOC] website: ir_actions: added some comments
[MERGE] Sync with trunk
[IMP] website: demo: set new demo as noupdate + updated some action name
[MERGE] [ADD] website: added support for calling a server action through a new controller, allowing to build website pages through server action.

website: added website/action/<id_or_xml_id> route, that runs the server action designed by its id or xml_id. Only published code server action are run. If the server action returns a response (for example the result of a template rendering), it is returned as result of the controller. This allows to have server action returning a rendered template, to display custom website pages based on some computation.

website: added an override of ir_actions_server:
- added website_published field: only published server action can be run + view update
- evaluation context gets request for evaluation, to enable request.render(template) or request.params.get(key) in order to retrieve the result of a form
- code server action returns 'response' the same way 'action' can be returned for classic code server action