Upgrade to handy-appbase, play2.2.  Partial commit.

This is the first commit in a fairly large set of changes.

The major change here is using handy-appbase (which gives us DataAction and allows us to remove a lot of duplicated code)

Some JSON APIs have changed -- particularly returning the object or array directly, rather than wrapped in an outer object. For example, returning an array of ContentEntries, rather than { entries -> [ ... ] }

The beginnings of a plug-in architecture are also included, as new ContentItems can register the handlers we need for their JSON and URLs.
Further work on upgrade and plug-in architecture. Partial commit.

This contains yet more changes related to refactoring the code to use DataAction, and introducing a basic plug-in architecture.

In this commit, the 'external' content items (web page, Google Slides, YouTube Video) have been moved out into a module.  This tests the basic wiring for ContentItem plugins.

There are also some javascript changes related to upgrading Angular.js.  Particularly, the SceTrustSrc controller is introduced.
Partial commit as part of the upgrade.  API now provides Mem, BroadcastStandard, and BroadcastUnique.