FR/BR: Scrolling MIDI display

[fromwithin]

This problem has been in for a long time so it would good to finally have it fixed.

In the MIDI editor, there are two completely wasted mouse buttons. left, middle and right buttons are identical, but the right button brings up a menu if you press it on a note (there is another bug, by the way, where the selection rectangle stays visible if you have dragged with the right button). It's such a complete and utter waste of the default features of the main input device. Just having the middle button map to smoothly scrolling up and down would be a massive improvement. Right button clicked on the MIDI backdrop to rotate between editing tools would be good too.

The middle mouse button drag on the keyboard to the left of the MIDI editor is broken. The mouse pointer changes to a hand, but does nothing. This occurs in both the in-line editor and the separate one.

And finally, can you please reduce the distance travelled in the MIDI editor when scrolling up and down with the mouse wheel (either hovering over the keyboard or with the Mouse Wheel scrolls MIDI grid option enabled. It jumps so much that it really affects workflow. Of course, this wouldn't be a problem if the middle mouse mapped to smooth scrolling.