Refactor UI test APIs

Refactored the UI test APIs:

- The UI APIs are used for creating users/groups/collabdocs/...
- Any JavaScript errors in the UI will be logged by CasperJS now, potentially giving more information about failing tests
- Exchange of information between UI and CasperJS happening through events
- More robust waiting for resources to get created
We should be calling this function with the various permutations to verify that all scenarios are working as expected. In this case, we should call it once for a group that has a description and once for a group that doesn't have a description.