Sjang92/advanced settings feedback

@jrbl  @njdup

There were no validations being done in Studio's course advanced settings tab. 
Now course instructors receive feed back as a list of settings changes that has formatting/value errors.

![screen shot 2014-07-16 at 4 13 13 pm](https://cloud.githubusercontent.com/assets/3598201/3606958/e8fe92b8-0d3e-11e4-8fe6-b861b0a8b3d4.png)

Actually, stepping through the code in the debugger, I am concerned that this method will now proceed if the advanced modules value is not a list (I assume before it threw an error because of the value not being iterable). This means that the code may end up removing tabs a few lines below, but we shouldn't be doing that since the new value will not/can not be saved.

If the value is not iterable, I think this method needs to immediately return or throw an error.