(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/ui2018/menus.ts

@@ -209,7 +209,7 @@ export function autocomplete(
 ) {
   return weasel.autocomplete(inputElem, choices, {
     ...defaults, ...options,
-    menuCssClass: menuCssClass + ' ' + cssSelectMenuElem.className,
+    menuCssClass: defaults.menuCssClass + ' ' + cssSelectMenuElem.className + ' ' + (options.menuCssClass || '')
   });
 }