Fill out obvious known fields in the data dictionary

Requires:

* https://github.com/hypothesis/lms/issues/4520
* https://github.com/hypothesis/lms/issues/4519

After we have a blank data dictionary, and some general guidance about data handling, it's likely that many fields in data dictionary can be marked as either safe for distribution or restricted.

We should:

* Note classes of data which we know are always, or never safe
* Mark such data up in the data dictionary
* Write what handling is required for fields which are not freely shareable and why
* Look for any obvious things we can fill out by common sense

We should not:

* Attempt to fill out every field