Engine update, and minor fixes

Hey everyone! I hope if that if you've been using SpritePile 2.0 that it has been a pleasant experience so far. I'm aware of some of issues people have been experiencing and I'm hoping this update addresses all of them. The initial release/hotfix of SpritePile 2.0 was on a semi-stable build of Game Maker Studio but since then they've cleaned it up a lot and so I spent some time upgrading this project to the latest version. You'll likely see some performance improvements! The rectangle tool also shows the current width/height, this feature will make its way into other tools pretty soon, but I wanted to rush out this engine update while I had time.