Add styling for clear button on search fields in table

Fixes [MLHR-827](https://malhar.atlassian.net/browse/MLHR-827)

![image](https://cloud.githubusercontent.com/assets/1390651/4801332/1c2cb370-5e31-11e4-8f79-6272a88c6339.png)

Also call setLoading for logical operators collection list.