Add support for reporting Field groups

Problem/Motivation

It would be nice to have a report that lists field groups in use in the site.
Items to show in the report:

1. Field group name
2. field group type
3. required
4. open by default
5. fields contained in the field group (all inclusive or by instance??)
6. entities using it. Maybe one row per entity... so it is easier to show fields containes ^^
7. description
8. tooltip description

Where should this live (path for the report)?

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes