Creation of prototype folder (self-contained prototype projects that are not production-ready)

This merge includes the prototype folder, which allows us to try out new ideas under less stringent requirements than for code that is posted to the primary project. Projects in the prototype folder should be self-contained, and should not be considered production-ready. Though we could leave the prototypes in a permanent separate branch, by merging these into the main branch we give everyone a chance to review and learn from them, while keeping the git learning curve as low as possible (i.e., we ensure that the prototypes are available locally to people, without requiring them to explicitly switch branches).