This lets you configure the ping interval for slaves via a
system property. (hudson.slaves.ChannelPinger.pingInterval)

The default ping interval has been lowered from 10 to 5 minutes.

It also moves the ping setup logic into a ComputerListener
(out of the JNLP slave Engine class). As a side effect, all
slaves will now have a ping instead of just JNLP slaves.

older plugins.

pushed the winstone dependency to the <dependencies> so that we can see the source code during debugging

earlier maven-hpi-plugin.

I think it's cumbersome to update the master POM every time we rev
maven-hpi-tools. I don't see why we can't set it here.

LDAP group names are now available as-is for the use in authorization. No upper casing / no 'ROLE_' prefix.