Display and dismiss completed games on Overview

Resolves #604.

http://jenkins.buttonweavers.com:8080/job/buttonmen-AdmiralJota/167/

Note: don't approve this until after cgolubi1's June pulls have all been merged.
The comment says "don't", but the function says "do".  Does this in fact work right?  (I didn't look at update_last_action_time() yet)