Add new resources via dropdown

Lots of links to create different types of resources were getting messy, so switched to a dropdown. Also wanted to refactor new and create controller actions to remove hardcoded references to classnames. These methods will now work even if class names change, or if resource types are added or removed.
When I create resources via the dropdown I get a URL that works but looks like: 
![screen shot 2014-08-17 at 11 15 42 pm](https://cloud.githubusercontent.com/assets/5882833/3944644/a116f0d6-2610-11e4-991f-3617c17eac92.png)

Pretty ugly! As a next step I want to use URLs like:
/resources/new/article
/resources/new/book

And so on. Maybe we can hack on this on Wednesday!