Fix preferences cache

* Fix the problem that preference cache was not reset when `setPreferredSomething` was called, only when `edit(preferred_something=)`
* Implement something more advanced than just `portal_cache.clearCache()` so that when a user change their preference, only preference of this user are affected.
* Increase default cache duration, now that we invalidate caches properly.

/reviewed-on nexedi/erp5!983