Adding Hook for Extra Submission Row Actions

Adding in a hook for extra submission row actions. I also took the existing functionality and hooked them in the same way so they can be unhooked or reprioritized. This makes things more modular (yay!)

![extra-submission-row-actions](https://f.cloud.github.com/assets/1065372/1925292/489616b4-7e2f-11e3-9a04-c05cb4a5468f.png)