Revised the tools for managing which FCurves are visible in the Graph Editor
curves area. Now, there are the following tools in place:
* V (channels region only) = Hide all curves except those in selected channels [OLD]
* H = Hide all selected curves [NEW]
* Shift-H = Show all previously hidden curves [NEW]
I've removed the old operator to toggle visibility status of selected curves,
as it doesn't seem that useful anymore.
fbd4dfb2c6