Compare Mode - Horizontal Screen Split

Adjust the ProofHQ Viewer to allow a horizontal screen split in the Compare mode. Allows one to compare versions in another perspective.

Very helpful when there is a piece with landscape orientation. Those are very difficult to review side-by-side because we must choose between looking at the entire page in a very small size, or looking at just a partial view of the page in a comfortable-to-read size. If we could look at them on a horizontally split screen it would be much better.