Ah! `mesh_additions.rb` modifies core API classes. Which is not good. I know it's part of old example files, but they where made before anyone had worked out best practices for the SketchUp Ruby API environment. We need to refactor this to comply with Extension Warehouse guidelines.

But let's do this after merging this. It's already a very big Pull Request. A refactor is better done separately. I can have a look at that when I get back home. As these old `rb` examples are something we shouldn't be offering.