Implement AppLauncher portlet-definitions as equivalent widgets

[apetro]

uPortal has an "App Launcher" portlet, typically configured with a title, icon, target URL, ... . There's a nice conceptual mapping to be had to an equivalent widget. Add sugar, support so that AppLauncher portlet-definitions are treated as link widgets when displayed in uPortal-home.

This might be an opportunity to refactor to use the AppLauncher configuration idioms so that these things are less different and more interchangeable.