(core) Simple localization support and currency selector.

Summary:
- Grist document has a associated "locale" setting that affects how currency is formatted.
- Currency selector for number format.

Test Plan: not done

Reviewers: dsagal

Reviewed By: dsagal

Subscribers: paulfitz

Differential Revision: https://phab.getgrist.com/D2977

app/client/models/DocModel.ts

@@ -111,6 +111,8 @@ export class DocModel {
   public pages: MTM<PageRec> = this._metaTableModel("_grist_Pages", createPageRec);
   public rules: MTM<ACLRuleRec> = this._metaTableModel("_grist_ACLRules", createACLRuleRec);
 
+  public docInfoRow: DocInfoRec;
+
   public allTables: KoArray<TableRec>;
   public allTableIds: KoArray<string>;
 
@@ -135,6 +137,8 @@ export class DocModel {
       model.loadData();
     }
 
+    this.docInfoRow = this.docInfo.getRowModel(1);
+
     // An observable array of user-visible tables, sorted by tableId, excluding summary tables.
     // This is a publicly exposed member.
     this.allTables = createUserTablesArray(this.tables);