Refactor components

Implement context mechanism to pass default attributes to descendant
components.

ui/notifications.js

@@ -4,7 +4,7 @@ import m from "mithril";
 
 const notifications = new Set();
 
-function push(type, message) {
+export function push(type, message) {
   const n = { type: type, message: message, timestamp: Date.now() };
   notifications.add(n);
   m.redraw();
@@ -14,8 +14,6 @@ function push(type, message) {
   }, 4000);
 }
 
-function getNotifications() {
+export function getNotifications() {
   return notifications;
 }
-
-export { push, getNotifications };