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/Timestamp.tsx

@@ -0,0 +1,66 @@
+import React from 'react';
+import classNames from 'classnames';
+import moment from 'moment';
+
+import { formatRelativeTime } from '../../util/formatRelativeTime';
+
+import { Localizer } from '../../types/Util';
+
+interface Props {
+  timestamp: number;
+  withImageNoCaption: boolean;
+  direction: 'incoming' | 'outgoing';
+  module?: string;
+  i18n: Localizer;
+}
+
+const UPDATE_FREQUENCY = 60 * 1000;
+
+export class Timestamp extends React.Component<Props> {
+  private interval: any;
+
+  constructor(props: Props) {
+    super(props);
+
+    this.interval = null;
+  }
+
+  public componentDidMount() {
+    const update = () => {
+      this.setState({
+        lastUpdated: Date.now(),
+      });
+    };
+    this.interval = setInterval(update, UPDATE_FREQUENCY);
+  }
+
+  public componentWillUnmount() {
+    if (this.interval) {
+      clearInterval(this.interval);
+    }
+  }
+
+  public render() {
+    const {
+      direction,
+      i18n,
+      module,
+      timestamp,
+      withImageNoCaption,
+    } = this.props;
+    const moduleName = module || 'module-timestamp';
+
+    return (
+      <span
+        className={classNames(
+          moduleName,
+          `${moduleName}--${direction}`,
+          withImageNoCaption ? `${moduleName}--with-image-no-caption` : null
+        )}
+        title={moment(timestamp).format('llll')}
+      >
+        {formatRelativeTime(timestamp, { i18n, extended: true })}
+      </span>
+    );
+  }
+}