Improve homepage

Currently the homepage is a list of reports in order of least recent to most recent.
Here are some changes we should make:
Also, we should try to group experiments by year. The list will only grow larger.

- [ ] Most recent experiments should be at the top.
- [x] Experiment links should also include the experiment description.
- [ ] We should group experiments by year as this list will only get longer.
- [ ] Don't include the index.html in the list of experiments.

I think doing this means we can also get rid of the behavior I don't like where experiment reports go in an "experimental" subdir by default. Instead they can go together and we can allow filtering by experimental.