Controller can't be set to watch only a specified namespace

[abayer]

Expected Behavior

You can specify that the controller should only be watching for CRDs in a specified namespace, rather than all namespaces, so that you can have multiple controllers in the same cluster. This was possible from 0.3.0 until 0.6.0.

Actual Behavior

From 0.6.0 onwards, you can't. =) Yes, I didn't notice this until way later. Whoops!

Additional Info

So #784 went in for 0.3.0, but #1015 refactored how the controller works significantly, and in the process, it lost the --namespace parameter. There's no way now (at least not that I can find) to have the informers filtered by namespace. It'd be good to get this back.