Expand/Collapse all accordions in PV

What the title says. Hopefully this is a useful functionality, and not that intrusive to the current design:

![screen shot 2014-05-26 at 11 06 39](https://cloud.githubusercontent.com/assets/6576325/3080904/7d2b1dcc-e4b7-11e3-80af-a39e9e05ae0d.png)