Curves view: Numerical entry

[timkang1980]

Having the ability to type in an input to see its output, or vice versa, would be really helpful in addition to the current mouse-browsing scheme. Mouse-browsing is fine but dependent on monitor/window resolution. This would help me in tracking precise input and output points.

Also - if I click the bottom readout in question, the colors disappear, and I can't get them back unless I toggle to a different pane and back. minor bug.