Fix "box" character in JPM repo view on Windows

The default font (Segoe UI) doesn't have symbol characters so the down
arrow next to a bundle/rev is just a box.

In the RepositoriesView swap it with an icon instead:

![image](https://cloud.githubusercontent.com/assets/114601/4010469/7e795706-29f5-11e4-8672-cc4822e66125.png)


Signed-off-by: Sean Bright <sean@malleable.com>