advanced search in classes screen (issue #23)

Setting up advanced search in classes screen. The search is done by class name, year, semester, professor, course name and enrollment (Issue #23)

![screenshot - 07222013 - 12 01 26 am](https://f.cloud.github.com/assets/1538066/832871/03c7886e-f27b-11e2-85b1-de378e9a5105.png)