(core) granular access control in the presence of schema changes

Summary:
 - Support schema changes in the presence of non-trivial ACL rules.
 - Fix update of `aclFormulaParsed` when updating formulas automatically after schema change.
 - Filter private metadata in broadcasts, not just fetches.  Censorship method is unchanged, just refactored.
 - Allow only owners to change ACL rules.
 - Force reloads if rules are changed.
 - Track rule changes within bundle, for clarity during schema changes - tableId and colId changes create a muddle otherwise.
 - Show or forbid pages dynamically depending on user's access to its sections. Logic unchanged, just no longer requires reload.
 - Fix calculation of pre-existing rows touched by a bundle, in the presence of schema changes.
 - Gray out acl page for non-owners.

Test Plan: added tests

Reviewers: dsagal

Reviewed By: dsagal

Differential Revision: https://phab.getgrist.com/D2734

app/server/lib/DocClients.ts

@@ -97,7 +97,7 @@ export class DocClients {
             if (e.code && e.code === 'NEED_RELOAD') {
               sendDocMessage(curr.client, curr.fd, 'docShutdown', null, fromSelf);
             } else {
-              throw e;
+              sendDocMessage(curr.client, curr.fd, 'docUserAction', {error: String(e)}, fromSelf);
             }
           }
         }