admin: tab system improvement, search: ?search qp

tab content classes (e.g. settingsList, activityList)
can implement "AsTab", "Navigatable" and or "PageEventBindable",
the first giving them a tab name, a subpath and a reloader function,
the second an "isURL" and "navigate" function for loading resources,
the last giving them bind/unbindPageEvent methods. These are looped
through in ts/admin.ts still crudely, maybe tabs.ts could accept "AsTab"
implementers directly.

"Search" class now has a ?search query param which just encodes the
search box content, set when you perform a server search (hit enter or
press the button). ?user queries from the accounts or activity tab will
be converted to this form on loading.

ts/modules/list.ts

@@ -110,7 +110,7 @@ export interface PaginatedListConfig {
     hideButtonsOnLastPage?: boolean;
 }
 
-export abstract class PaginatedList {
+export abstract class PaginatedList implements PageEventBindable {
     protected _c: PaginatedListConfig;
 
     // Container to append items to.