Wicket: UI screen for update images

[andrewjstone]

We want to be able to ingest rack updates, read the manifest and display what's available for update. There should be some mechanism to show what's on the rack already and initiate updates as well.

[andrewjstone]

Most of this is done. There's an update that shows live status for each artifacts update in #2555.

I'm going to close this and open a few more specific issues.