Re-implementation of manage feeds dialog

I wound up re-implementing the manage feeds dialog using an AroundList instead of a DataRepeater and collections.
The reason for doing this is that DataRepeater does not support swipable at this point, so I needed to use an AroundList to implement swipe to delete functionality.

As a side effect, the new feed section is now at the top of the dialog. This is because aroundlist only supports content above the list. It looks like there is initial support for content below the list, but the list currently just renders over top of this content.