[WIP] Add prometheus monitoring to barn-hdfs

What do you reckon to this monitoring?

I've got an instance running in cloudmaker, you can see the data at: http://10.70.9.147:9090

@brapse 

Along the way I've found out that, some of which I'll try and make into jiras eventually:
1) we can probably make it a bit simpler to deploy barn-hdfs by getting it automatically publish the correctly named .zip to maven probably, you need to do manual things at the moment,
2) there's something called loggen you can use to generate test logs, there's the remnants of its use by omid, we could re-set-it-up so it's use to use
3) you have to be careful when setting up test stuff in cloudmaker, because a lot of the chef stuff is hardcoded (so it starts using prod barn-hdfs and prod hdfs), we should probably fix that :-)
4) barn-hdfs is run on java 1.6, using the custom jre thing omid setup
When I set it I calculate the age with a now - epoch_date. (see the setMinFileDate function)