Add maps to server config page

[Joe-Klauza]

The server config page should include a maps section which should work much like mutators section.

• Toggles for each map+side combination where appropriate (no Insurgents side for Frenzy)
• The selected maps generate a MapCycle.txt for the server using the configured game mode
• The MapCycle.txt textarea at the bottom of the page should still be usable, since some servers may want to allow the map vote to change the game mode. As such, the textarea's contents should be concatenated with our generated MapCycle.txt and then duplicate entries should be removed.