Open Games page

Resolves #75.
Resolves #185.

http://jenkins.buttonweavers.com:8080/job/buttonmen-AdmiralJota/101/

The UnusedLocalVariable warning is the same one that I explained over in #862; I manually copied a couple of support methods from that branch over here, and will do my conflict resolution penance when the time comes.

#185 does also mention the possibilities of more complicated choices -- specified button subsets, randomized selections -- but I think those things best fall under other tickets.

(Also, this is dependent on #870, of course.)

(Note that this allows a query string parameter from the URL to be parsed as a player. I think this should be safe.)