Add local service implementations to support client-side-only use of App Inventor

[ewpatton]

This is pulled over (with modification) from the Aptly on a phone demo. This PR adds a build flag local.services that when set to true in an ant invocation, e.g., ant -Dlocal.services=true noplay will bundle versions of the UserInfoService and ProjectService that run entirely client-side. To do this I have implemented a GWT wrapper around the JSZip library so that we can unpack AIA files in memory on the client side and store those in a hash map similar to how the Datastore works.

This is a work in progress. The following still need to be done to create a robust solution:

• Assets are not handled, either upload or download
• Still need rendezvous server access (in Aptly we 'rendezvous' through API calls from the Swift code)
• Export project support in the UI (in Aptly we export ZIPs by callback to the Swift code)
• Extensions are not yet supported and the ComponentService would need the same treatment