Here's the beginning design.  Since it's a high priority, I didn't want to wait too long to show you something.  As you can see, I still had a lot of questions and things I wasn't sure about.

I have some tests, but wanted to have it more complete before submitting it.

When you said 'submit', I didn't know if you wanted a real PR at each step or just files here.  If you'd prefer a PR so you could modify it, let me know and I'll prepare that tomorrow.

Thanks!