When clicking on the app website admin with the arabic language,
it raised an error because this.date_from.format('YYYY-MM-DD') in
function fetch_data returned an arabic date "٢٠١٧-٠٧-٠٥".

opw:751960

 * Set the blocking warning if the user enters a 'Client ID' without
   any 'Tracking ID'.
 * 'Google Analytics in Dashboard' field is visible only if
   'Google Analytics' is checked in website settings.
 * Get/Set the value of 'google_analytics_key' and
   'google_management_client_id' from 'website' model instead of
   'ir.config_parameter' on 'Google Analytics' wizard.
 * If ID is set on 'Google Analytics' wizard then activated the related
 features and populate fields in website settings.

It now update the website settings parameter use_google_analytics_dashboard
so that the settings are correctly updated with the user choice.

Implementation is changed so that the dashboard uses a jsonRpc call instead
of directly calling ir_config_parameter set_param.

The RPC system was not completely satisfactory, we decided to prepare
the future and do it properly.  This commit introduces the new rpc
system, which replace the previous new one.  We now simply have a
method, this._rpc, which takes a dictionary of parameters.  The idea is
that depending on the parameters, it is able to add correct default
value when necessary.

For situations where we don't have the this._rpc method, we can use the
rpc.query method, which takes the same arguments, but directly calls
ajax.rpc instead of triggering up some events.

The _rpc method is now the preferred method to do a rpc, so we need to
update all calls.