Trackers

This adds:

* a list of all open trackers sorted (initially) by (target milestone, priority) to the project details page
* for each tracker, you can click on "Details" and get the bug details in ernest
* adds breadcrumbs navigation to the tops of pages for easier navigation

Issues:

1. this is pretty ugly. srsly.
2. the list of trackers on the sprint details page is pretty crazy for sumo. i suspect we could spend some time cleaning up the data, but i wonder if there are better ways to organize and display the list of trackers
3. the bug details page for a given tracker shows the list of bugs that are being tracked, but ... there are probably things we can do here to show progress and other things better
4. the breadcrumbs navigation takes up a lot of vertical space which sucks, but i kind of think we benefit greatly from having a breadcrumbs navigation given that this is hierarchical data; i know it helped me a lot while testing

Anyhow, thoughts? r?