added jcollect network listener collector

This collectors is able to receive metrics from one or more jcollectd instances. It has an UDP listener in a seperate thread for this purpose.

Jcollectd can run as a java agent inside an JVM and gather metrics from mbeans. Normally jcollectd sends its data to a collectd server, but since the protocol is open and python code was available I made a Diamond collector.

Background info:
* https://collectd.org/wiki/index.php/Plugin:Network
* https://github.com/collectd/collectd/blob/master/contrib/collectd_network.py
* https://github.com/hyperic/jcollectd instances