QE Doc flow

- Three top level (or close to it) docs
 - How to guide on QE configuration
 - QE field guide (moved out of model field ref to its own section)
 - Topic guide on QE usage

- Planning to finish QE setup in the how-to doc then switch back to the
  topic doc to explain the workflow.

In the QE topics guide I'm going to explain how to develop a patient model
similar to the Python QE tutorial and the encryption test suite.

If embedding were possible now, I could present the same example. Since
embedded models are a WIP I may either:

- design the guide to work around that issue
- design the guide to anticipate resolution of that issue

In ether case, I'll try to wrap this 24-48 hour docs jam having covered
everything I know about QE and Django and having presented it to Django
folks in a way we can support.

- Configuring the encrypted_fields_map section