Fix keyboard shortcuts

The down arrow does two things, either U-turn or move the drone view. Kind of dumb to have that because it’s easy to end up in the bird’s eye view and do a u-turn when trying to move the camera. The U key doesn’t do anything and is a pretty logical choice for a u-turn.

Add a shortcut key to get to the settings menu, it boggles my mind that there isn’t one, anyone that is using the minimal UI with the zwift prefs is stuck with whatever trainer difficulty they are in at the time.

Seems like a bit of an oversight…