Fixed UriMatcher to match root paths.

1.  Existing ShadowUriMatcher does not match root paths, as the Android UriMatcher can.
2.  Existing ShadowUriMatcher does not match Uris as the Android UriMatcher with respect to the order in which addUri with wildcards is called.

The Android UriMatcher class is fairly small.  I just adapted the Android API 16 code and adapted the existing tests.  

I also removed a couple of existing tests that were testing the existing shadow implementation, and not it's interface.  Obviously, these tests no longer passed with a different implementation.