Add mode for vertical bar to scroll rather than music

[aspiers]

Rather than having the staff horizontally scrolling left past a fixed vertical bar, there should also be the option of having the staff stay still and the vertical line scrolling right. When it reaches the far right of the screen, the staff would refresh to show the next few measures of music.

Some thought would be needed to ensure this happens in a visually intuitive manner e.g. the refresh should perhaps happen just before the line reaches the right hand edge, since humans always read slightly ahead. Also it might make sense to align measure breaks with the left and right-hand edges of the video, although that could pose other problems.

[aspiers]

After further thought, I'm not sure how useful this would be. I guess the main advantage is preventing that sea-sickness kind of effect where the music appears to scroll in the opposite direction at the end of a video you've been staring at for 5 minutes.

[aspiers]

Actually the constant changes in pixel scrolling speed due to different length notes and changing tempos makes this more worthwhile than I thought. Moving to 0.3.

[aspiers]

Fixed!