Finish new Message component, integrate into application

Also:
- New schema version 8 with video/image thumbnails, screenshots, sizes
- Upgrade messages not at current schema version when loading messages
  to show in conversation
- New MessageDetail react component
- New ConversationHeader react component

ts/components/conversation/ResetSessionNotification.tsx

@@ -0,0 +1,19 @@
+import React from 'react';
+
+import { Localizer } from '../../types/Util';
+
+interface Props {
+  i18n: Localizer;
+}
+
+export class ResetSessionNotification extends React.Component<Props> {
+  public render() {
+    const { i18n } = this.props;
+
+    return (
+      <div className="module-reset-session-notification">
+        {i18n('sessionEnded')}
+      </div>
+    );
+  }
+}