Summary:
This allows `*SPECIAL:AccessRules` to give read access to the access rules to more users, and `*SPECIAL:FullCopies` to grant download/copy rights to more users.
This diff also changes forks to be owned by the user who forked them (previously they were an editor), since that feels more natural.
Test Plan: Added and updated tests.
Reviewers: dsagal
Reviewed By: dsagal
Differential Revision: https://phab.getgrist.com/D2760
