Adjustment to sort property UI on case list page

[Ticket](http://manage.dimagi.com/default.asp?146720)

##### Changes
- "Add sort property" and "Add filter" clickables are now styled as buttons.
- Sort property list now functions like the case property list. Each time the "Add sort property" button is clicked, a new row is added to the list. Previously, it used a "template row" that always existed in the table. 

###### Before
![screen shot 2015-01-01 at 1 04 12 pm](https://cloud.githubusercontent.com/assets/2117127/5592045/d21a1e1c-91b6-11e4-922a-b36c03c292b3.png)

###### After
![screen shot 2015-01-01 at 1 03 52 pm](https://cloud.githubusercontent.com/assets/2117127/5592047/dfbe7fe0-91b6-11e4-88b1-502ced1fd503.png)


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