Corrected Graphite Handling in metricKeys 

Hi,

I was tinkering around with the metric index creation on our local installation and I adapted the metricKeys controller to handle multiple graphite data sources without crashing. I'm not entirely sure if this is the best way to implement this, so feel free to show me better ways - I'm not very experienced in javascript. :)

I didn't commit my changes to the settings component to get the name of the metric index from the config file, or the view since currently, the evil red button just spends almost an hour stuffing metrics into elasticsearch and it doesn't look like we get anything from it yet, so I don't think it's useful to let users waste time.