plugins like the rebuild plugin that want to default the parameter input fields with
a previous set of parameter values.  Currently the rebuild plugin has to rewrite the
parameter input display for each core parameter which prevents it from supporting
additional parameter types outside of core.

[FIXED JENKINS-9122] - Archived artifacts overridden when having multiple produced artifacts under different paths but with the same file name

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.