Fix histogram bin sizing controls

Addresses #1769 

The keydown event handler for the bin size text box used weird, non-standard ways of getting event info.  This is no longer the case, and that works properly

I also turned the bin size slider around so that when you move it to the right, the bin size goes up.  I was trying to change it so you would change the number of bins, but after thinking about it, that doesn't seem as useful as changing bin size.