Query support

Ticket: #377 
This adds query support as described on http://wiki.vg/Query
Tools for testing can be found on the bottom of said page.
Unit tests are available on the [`query-test`](https://github.com/Johni0702/Glowstone/commits/query-test) branch. I didn't want to include them in the PR yet because they depend on mockito and powermock.