Disable value caching in CPControllerSelectionProxy

[Klaas Pieter]

I'm going to push a commit in a second that will disable value caching
in the CPControllerSelectionProxy.

I'm going to disable it because it doesn't handle keypaths. For
example if the key department changes, the cache for
department.whatever should also be cleared.

The caching saves some time because in stead of having to perform
valueForKeyPath: again, it can just get the key from the cache. The
time it saves depends on the length and the number of key paths that
are being observed.

In most cases keys will be bound correctly and there will not be a
significant amount of keys bound. Because of this I think refactoring
the caching to work with key paths will be a premature optimization.

For now the caching will be disabled, if anyone is having performance
problems because of it please let me know and I'll look into it again.

- Klaas Pieter

[Klaas Pieter]

For future reference, the commit is here:
https://github.com/280north/cappuccino/commit/8345788e59cc6a00500b7a48cc2e8e59a7da7fbf