Compare: Apply common keyboard shortcuts to compare window

[DawMatt]

Hi,

The Compare window would be easier to use if certain common keyboard shortcuts were available in it. The main shortcuts to be applied would be:
- zoom shortcuts (+ and - to increase and decrease zoom).
- next file shortcut (space bar, or alternatively arrow or page up/down keys)

These are used elsewhere throughout the program so consistent application of these shortcuts would improve usability and intuitiveness of the application.

Thanks,
Matt