Apply changes to the search settings form.

#5481 

This PR addresses https://github.com/openscholar/openscholar/issues/5481#issuecomment-47363132

Output after changes:
![selection_284](https://cloud.githubusercontent.com/assets/4497748/3422701/eaf87bfc-ff5a-11e3-863e-25ab84e00f1c.png)

Note:
In the comment above @tcheng001 is asking for the use of select2 for the sites. This is already the case. The reason it's not working with the select2 for now is related to the moving of the JS to the bottom of the page in ``os_js_alter()``.