"Add Trackers" form. PMT #95578

Adds an "Add Trackers" form just like in PMT.

![screenshot from 2014-08-18 17 23 49](https://cloud.githubusercontent.com/assets/59292/3958225/f82e7340-271d-11e4-9ac9-5bc4eee345d5.png)

You get here from the "Add Trackers" link from the front page. I'm open to other suggestions of where to put this.