Add pivot options for mirrored mouse coordinates/view alignment

[odraencoded]

In the mouse options, it would be interesting to extend the pivot settings to include "mirrored" coordinates.

With a mirrored mouse pivot, when clicking on the top right corner of the view, for example, the pivot would be the bottom left corner. This would allow the mouse coordinates option to be meaningful in mouse handlers where it would be otherwise meaningless.

(The stretch mouse handler can't use mouse coordinates because you can't zoom out with it, only zoom in.)

Also I want to see what it would be like.