Add 'Set Hyperspace Target' button on mission screens.

As the title says, I added a button on the mission screens that will set the players hyperspace target to the mission location StarSystem. I attempted to add it in InfoView.lua, but couldn't make room on the screen for it. Although, I am running at 1024x768 resolution so I'm sure it's not as bad on higher resolutions.

I'm not very happy with how it looks, however. It seems kind of out of place. 
![image](https://f.cloud.github.com/assets/2941180/144452/bf69bb74-741c-11e2-85b9-0ba72534da61.png)


Ideas on how to improve this are very welcome. 

Included in this PR is a commit adding a font argument to the SmallLabeledButton, I found it useful for making the text smaller, as far as I know, you can't call :SetFont() on it. But I'm not sure if it needs to be in here.