Visual theme selection

The latest release featured a visual theme selection and also a new theme bringing the count up to 10 available color themes. Everyone should be able to find something they like.

With this release I also took the opportunity to update the screenshot images for the product page in the app store. This is one of the things I don't like about the app store, you have to make a new release if you want to update the screenshots. Feels a bit clunky to me.