[ADD] web: handle custom_events perform(_model)_rpc
[ADD] web: handle custom_events perform(_model)_rpc

If those events are catched by the web_client, it means that no other widget
did handle them, so simply call their on_fail callback.

ygol/odoo,hip-odoo/odoo,ygol/odoo,dfang/odoo,hip-odoo/odoo,dfang/odoo,hip-odoo/odoo,ygol/odoo,dfang/odoo,hip-odoo/odoo,dfang/odoo,dfang/odoo,ygol/odoo,ygol/odoo,ygol/odoo,dfang/odoo,hip-odoo/odoo,hip-odoo/odoo,ygol/odoo