Mousing over a graph label should bring the corresponding line to the "front"

[thepaul]

For example,

I'm pretty sure the line for "success" is just hidden behind the line for "total", but it would be nice to make sure. If when mousing over the "success" label in the graph legend, the line for "success" should be drawn on top of the one for "total". This would also be helpful for graphs which have a large number of component metrics, even when the lines don't necessarily overlap.