Tidy up heading and table styles for big lists

* Move create actions beneath heading (and warning when there is one)
* Make table more legible using borders and table heading styles — clearer divide between columns, clearer headers, clearer table boundaries
* Remove empty nav container

Before:
![screen shot 2014-09-05 at 10 03 42](https://cloud.githubusercontent.com/assets/319055/4163628/a58d58e8-34e9-11e4-94a5-ca7174a0bcd1.png)
![screen shot 2014-09-05 at 11 43 32](https://cloud.githubusercontent.com/assets/319055/4163627/a58b7488-34e9-11e4-808f-1de38f65e325.png)
![screen shot 2014-09-05 at 11 43 17](https://cloud.githubusercontent.com/assets/319055/4163629/a58ddcb4-34e9-11e4-86ef-650a26c443d3.png)

After:
![screen shot 2014-09-05 at 10 03 33](https://cloud.githubusercontent.com/assets/319055/4163631/b2761ea0-34e9-11e4-8841-e928d0a87e3a.png)
![screen shot 2014-09-05 at 11 44 10](https://cloud.githubusercontent.com/assets/319055/4163633/b285763e-34e9-11e4-8cb4-8e6b8a238a3b.png)
![screen shot 2014-09-05 at 11 43 40](https://cloud.githubusercontent.com/assets/319055/4163632/b27bbcca-34e9-11e4-8e2c-0718d702f11d.png)