[dev] Permissions cache

[Chuck Hagenbuch]

Quoting Duck <duck at obala.net>:

> I was trying to find out a betters solution for the permission system today.
> While I was trying to figure out possible solutions, one thing come to my
> mind. Why we don't cache the permission data? Permission data generally don't
> change some often. As I see in the applications usages it will be enough to
> cache the getPermission() and exists() methods. Even solutions like phpGACL
> cache this data.

Probably just no one has had time to do it. Caching seems like a  
perfectly good idea to me as long as we can invalidate the cache on  
the proper events.

-chuck