Compress all PNG images.

Used [TinyPNG](https://tinypng.com/) to compress all PNG images in the project, with the device images being the main focus. It reduced the device image file sizes by an average of 72%.

It'd be nice to automate this for the repository, but I figure the images won't change much if at all. And people are more likely to use the provided PNG device images than exporting and compressing them themselves. Plus it saves a step.