Update section about Central web user roles

The section about Central web user roles lists the actions that each role allows. However, I think some actions are missing. For example:

- Set up usage reporting
- Stop usage reporting
- Actions related to datasets. Most importantly perhaps, Data Collectors can only read a dataset's entities indirectly, that is, only if the dataset is attached to a form.

Start by locating the Central web user roles section in the documentation and review how it lists each role's permitted actions. Compare the list with usage-reporting actions and dataset access, especially the indirect access available to Data Collectors. Done means the section accurately documents these missing permissions and the dataset limitation.

Written by the indexing model from the issue text.