Bug XXX - Add PICL Android Account type.
Bug XXX - Merge seanmonstar's PICL Sync demo.

This:
* fleshes out a potential PICL global session hierarchy;
* starts work on HTTP PICLTabsClient;
* syncs against Fennec's tabs content provider;
* syncs against live servers.

The tabs content provider part needs a tiny Fennec patch to look
better in the Android Accounts menu, but this will actually sync on
the emulator and on newer Android devices.