more fun with cache

Pathnames are now being cached. But unlike cabinetForRole, a role's pathname changes over time and the cached value can become invalidated for any number of reasons.

The advantage of caching pathnames comes when displaying lists of pathnames. And I suspect little advantage can be realized without a fairly large cache size. Fortunately pathnames are small, so we can have that large cache.

And yes, this is a prelude to caching topics.

Bill