Manage the white-list, banned-ips, and banned-players files.
Rebase configuration on top of the default server.properties.

The server.properties.erb template was based on whatever I happened
to be doing at the time. This commit rebases it on top of the
default file for 1.7.2 as defined by the wiki.

http://minecraft.gamepedia.com/Server.properties

Deviations have been exposed as configuration parameters.

* spawn_protection
* public
* difficulty
* white_list
Add support for modifying the server-port config parameter.
Add support for modifying the max-players parameter.