Caret affects test identity

[eddyashton]

If I have a metric called "Foo" that should have been called "Foo^" (because I realised after running it for a while that it was showing increases as RED, and I want them GREEN), then ideally it would continue to use my old numbers and just redraw the graph with the correct colours. However, it currently views this as a new metric, so draws it on a blank graph.

[achamayou]

If we go down this route, I suggest we get rid of the "^" hack altogether, and pass an explicit direction= attribute instead.

The only reason this was done with "^" and hiding it at display time was expediency.