Summary:
- Added fields to _grist_ACLRules for the new Granular ACL representation
- Include a corresponding migration.
- Added ACLPermissions module with merging PermissionSets and converting to/from string.
- Implemented parsing of ACL formulas and compiling them into JS functions.
- Add automatic parsing of ACL formulas when ACLRules are added or updated.
- Convert GranularAccess to load and interpret new-style rules.
- Convert ACL UI to load and save new-style rules.
For now, no attempt to do anything better on the server or UI side, only to
reproduce previous behavior.
Test Plan: Added unittests for new files; fixed those for existing files.
Reviewers: paulfitz
Reviewed By: paulfitz
Differential Revision: https://phab.getgrist.com/D2664
