Create UI controller for view models of tracked items

Simplify the logic necessary in the UI by creating a UI controller
which returns view models that can easily be consumed by the UI.  This
controller will return the tracked items by category, which allows the
UI to iterate over those categories dynamically when building the page.
Add another category, fix a couple problems

Add camera and video category, along with special logic for finding
item details in that category.

Also set the URI correctly in the item details.
Update UI for tracked item

Add some additional logic to improve mobile display.  Make sure to show
all past prices.