[AD] Add initial set of Android Contacts provider tests
Let Query<T> handle a null execution return

Primarily a change for the way we're doing testing on expressions in the
android tests.
Remove unused column list
[AD] Improve content query translator

- Fixes some query construction errors (fixes #26).
- Fixes AND/OR expression handling, was mistakenly handling And/Or instead
  of AndAlso/OrElse.
- Fixes falling back in scenarios where it wasn't required (two conditions
  on the same mimetype).