CYB-198 - Gallery - accessibility / design / routes changes

https://jira.ets.berkeley.edu/jira/browse/CYB-198

* Accessibility: add labels for dropdowns
* Design: Make headers the same across tools
* Simplify hover / focus & make it work for images
* Background-size: 100%
* Update Paths
Merge pull request #103 from christianv/CYB-198

CYB-198 - Gallery - accessibility / design / routes changes