Fix page-actions buttons line wrap in admin

We had a problem in the admin where the page action buttons would overlap each other if there was a long product title.

![before](http://i.hawth.ca/s/1s3Zqj7D.png)

This can be fixed by giving these buttons a line height.

![after](http://i.hawth.ca/s/pamxp2UD.png)

All buttons are also given `white-space: nowrap;`, as the buttons do not look correct split across multiple lines.

![broken buttons](http://i.hawth.ca/s/QQcGl1Z3.png)

I tested this on chrome, FF, IE9, and IE10. I believe this cleanly applies to master, 2-1-stable, and 2-0-stable.