CYB-368 - Gallery: browser back button in item detail view doesn't return to gallery main

https://jira.ets.berkeley.edu/jira/browse/CYB-368
I think there are a number of usability issues with the current experience:

- When I click on a user's name, it takes me to the gallery page with the name of that user as a filter. When the user hasn't uploaded anything, it's completely empty and it looks like something is missing. I think it would be good to show an empty message when no results are available.

![screen shot 2014-12-15 at 2 24 56 pm](https://cloud.githubusercontent.com/assets/109850/5445122/2c6b160e-8466-11e4-9cb4-daef87f86ab7.png)

- In the above scenario, when I click the previous button once, it takes me to the item page (as expected). However, when I hit the previous button again, it sends me back to the gallery with the username filter still there (even though I started from an unfiltered list). I think this is unexpected, and would be best resolved by encoding the filters in the URL. However, that would mean that we need to move away from searching immediately when entering a user name to searching through a submit action.

@elicochran : Any thoughts on these issues? If we'd like to implement these suggestions but don't want to hold up this PR, I'd be happy to have a go at them as part of the 1.x release.