Rework how mark2 properties are defined.

There are to many possible settings you can use for mark2 to try and
list all of them out. There are three hashes you can use to tweak
mark2.

minecraft['mark2']
minecraft['mark2']['java']
minecraft['mark2']['plugin']

These will get divided into sections in the configuration file
in case you ever have to read it.

To change settings you just create a hash of settings. For example.

node.set['minecraft']['mark2'] = { 'shutdown-timeout' => 60,
'log.rotate-mode' => 'daily' }

For plugins it may look like this.

node.set['minecraft']['mark2']['plugins'] = { 'backup.enabled' =>
false }

java.cli.X.ms and java.cli.X.mx default to minecraft['xms'] and
minecraft['xmx'] settings from the default attributes file.