Draggable Camera Middle Move for Magic Mouse & Trackpad

@bodysoulspirit, yes, I’m thinking we’d add a keyboard-mouse combination to enable Make Draggable Camera to move through the scene without needing a physical middle button.

USB HID will enable Vuo to receive data from more USB devices (e.g., game controllers, SpaceNavigator), but it won’t affect support for existing devices like mouse/trackpad.