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)

```update_from_dict``` has a nice declarative name, and I'd like to see it behave unambiguously. I'd prefer if here you did something like:
```
updated_data = None
if did_validate:
    updated_data = cls.update_from_dict(key_values, descriptor, user)
```
and then update_from_dict could stop taking the did_validate parameter and associated conditional.