Add ``featured_list`` in the app_list context.

https://github.com/madewithbytes/us_ignite/issues/234
Use generic featured item in the app list.
Add featured events to the context.

https://github.com/madewithbytes/us_ignite/issues/234
Add featured hubs to the context.

https://github.com/madewithbytes/us_ignite/issues/234
Add featured resources to the context.

https://github.com/madewithbytes/us_ignite/issues/234
Update tests to reflect context updates.
Serve only valid entries in the map.