Summary:
- Add headers to tables.
- Change styles to reduce boxes-within-boxes.
- Add validation of table and column IDs, both in UI and on server when saving rules.
- Add autocomplete for tables/columns used for UserAttribute rules.
- Add a fancy widget to set permission bits.
Test Plan: Updated browser test for new UI, added a test case for user attributes.
Reviewers: paulfitz
Reviewed By: paulfitz
Differential Revision: https://phab.getgrist.com/D2695
