Ability to reset page (cell) when unpresented

[ddcrobert]

Here's a small commit to enable cell resets.
E.g. the user zooms, then he swipes to the next page, the former page one is reverted to original format.

[ranunez]

Thanks for this PR @ddcrobert! Can you please provide a little bit of background as to the use case for why this is needed? Thanks!

[ranunez]

This looks good, thanks @ddcrobert!

[ddcrobert]

Thanks! The PDFs I use are newspapers. The reader has to pinchs and pans over it in order to read articles.
Here's a sample scenario: the user reads a page (assuming its LTR), at the end of the page he's at the bottom right, he pans a bit to jump to the next page, etc. If he wants to come back on a previous page, all pages would be zoomed in, so it would require way more pans to get back. In short, its about having a user-friendly navigation, like you would turn pages.