Use UIManager for undo/redo of crop/delete/insert

[theerfan]

Without that, they'll get mixed up and it'll keep making new pdfs. We don't want that.

[theerfan]

The cmd command works now, but the undo doesn't. [For our new classes, PageOrganizer and Crop]
Need to look at the trace to see where the undo command doesn't get added.

[theerfan]

Also, as we're trying to keep the annotations on insert/delete page commands using the setAll function, note that the annotation does get moved but is invisible, and the number of pages on which the annotation gets put on doesn't get adjusted.

So:

1. Look up how pdf.js shows the elements relating to those annotations and make them visible/create them again
2. Try to change the objects you get from the getAll method to adjust for the pages/