[IMP] website: snippets: add resize bar on snippet overlay; resising % 8px; remove size class
[FIX] website_event: filter on events
[FIX] events yaml test, remove event.on_change_address_id

on_change_address_id was used to populate "display" address fields
from the address m2o. The address fields were removed in favor of
using show_address (in the context), leaving an onchange called
returning fields which don't exist in the view, thus crashing the
corresponding yaml test (which checks for that).

Since the onchange has no purpose left, remove it and its call.