Segmentation Improvements

I think there are some improvements to be made in the Segmentation engine.

• Cannot do segments within segments.  This really limits our ability to manage custom audiences and merge them together as necessary for guides or other purposes.
• Can AND and OR criteria, but cannot do something like this: "target engagement to users who visited NewsCenter feature < 5 times within the last 30 days."  Can only do: "NewsCenter feature < 5 times", "Visited anywhere in product within 30 days".

Thanks for listening!