Add feature: Clickout on graphs

I created a patch that allows linking data-points on graphs with urls.
Currently you have to first set the URL in the General-tab and add data-specific parameters you want to include in the Clickout-param-field in the metrics/query-editor mode.

Example:
General->Title: Memory/CPU
General->URL: http:/example.com/processes.php
Metrics->clickoutparam: server=$server&type=cpu_idle
would send you to: http://example.com/processes.php?title=Memory%2FCPU&time=1415201533000&server=1&type=cpu_idle