(core) Improve the UI for ACL rules.

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

app/client/models/entities/ColumnRec.ts

@@ -81,8 +81,7 @@ export function createColumnRec(this: ColumnRec, docModel: DocModel): void {
   this.disableModify = ko.pureComputed(() => Boolean(this.summarySourceCol()));
   this.disableEditData = ko.pureComputed(() => Boolean(this.summarySourceCol()));
 
-  this.isHiddenCol = ko.pureComputed(() => this.colId().startsWith('gristHelper_') ||
-    this.colId() === 'manualSort');
+  this.isHiddenCol = ko.pureComputed(() => gristTypes.isHiddenCol(this.colId()));
 
   // Returns the rowModel for the referenced table, or null, if this is not a reference column.
   this.refTable = ko.pureComputed(() => {