accounts: pagination, server-side search

Pagination fully factored out, and both Activities and Accounts now use
a PaginatedList superclass. Server-side search is done by pressing enter
after typing a search, or by pressing the search button. Works on
accounts, soon will on activities if it doesn't already.

ts/modules/tabs.ts

@@ -1,7 +1,5 @@
 import { PageManager, Page } from "../modules/pages.js";
 
-declare var window: GlobalWindow;
-
 export interface Tab {
     page: Page;
     tabEl: HTMLDivElement;