update course_management_renderer BS2 grid generator functions to BS3

This issue was opened in elegance and again in my fork of elegance.  Moodle core course management renderer outputs BS2 code.  This updates it to BS3.
before:
![before](https://cloud.githubusercontent.com/assets/743499/2966575/31e393ea-db15-11e3-8dc9-cbfb6f160dfa.png)

after:
![after](https://cloud.githubusercontent.com/assets/743499/2966578/3960b134-db15-11e3-899d-bac078f9e3be.png)

would have been cool if they'd used this as a core_renderer() upgrading would have been super easy...(er)