Account selector rework.

- Show email address
- Show inbox unread message count

Initially I thought of using a join to get accounts with their unread
counts with one query, but there were enough subtle issues that I gave up
on the idea.

Instead it uses a MatrixCursor to build a completely new cursor,
based on a regular accounts cursor.

Change-Id: I09e8762f131cc2bd3637e1a3d302088a3b5b2479
1 file changed