Lea add donation levels to projects

In setting up balanced payments, I had to do a bunch of work that should be separate branches. So I'm teasing out the individual parts and creating branches for them. Here's the first: add donation levels to projects.
Good point - right now, they're just forcing a new line in the UI. I haven't decided what to do for styling, yet. When I get to the next round of css, I'll keep this in mind. Thanks!