1. add geo_position field;
2. support list anno by create time;
3. support list anno by latest update;
4. support list anno by vote number;
5. support list anno by activity number;
6. support list anno by flag number.
Merge remote-tracking branch 'upstream/master'
Merge pull request #57 from topcircler/master

geo_position; anno list by criteria
Merge remote-tracking branch 'upstream/master'