Add tooltips with parameters to dependency graph.

![tooltips-ss](https://f.cloud.github.com/assets/2633943/750446/679e3d06-e4ca-11e2-9472-209243fb57a7.png)

Not sure if all of the front end cruft is needed. Maybe @wwajerowicz  could confirm? I had to do some cherry picking to get out the right commits, so I'm worried I may have accidently missed a few.