Collections Update

It's finally done \o/

As the name implies, the collections update introduces the new feature of collections.
Collections allow bundling images together in an ordered fashion. They are ideal for comics or magazine scans, but should also be useful for various other collecting needs. 

Along with this new feature come a whole lot of internal changes and fixes. Including but not limited to a large performance boost and lots of small UI improvements.

Next up: documentation.
This program has grown to the point where it really needs some sort of guide, so that'll be in the next update.