Change archive icon and clone panel styling.

This request changes the archive icon to the archive icon rather than the book icon (archived support added via PR #5841).

It also adds a vertical line between the clone panel buttons and changes the cursor from the "not-allowed" cursor (set by bootstrap via the read-only property) to the default cursor. Although it cannot be seen, it also extends the SSH and HTTP(S) buttons to the "borders". The old style had some null space around the buttons. This styling _does not_ change the color of the active button as my previous pull request did.

# New Styling
![styling-changes](https://f.cloud.github.com/assets/2117996/1767449/212cc894-6754-11e3-9c0b-391661cc5bd8.png)