Turbo Render (#298)

* More responsive React updates on scroll

* `Icon`s now use shadow dom

* Faster Sparkline

* Recycle table rows

* Separate Header from Chain to avoid vdom diffing

* Separate THead from Row.HEADER to avoid vdom diffing

* Throttle rendering updates on chain tabs, also styles

* Minor tweaks and fixes

* Created components for all columns

* Wrapping up Column refactor

* Rename Row--td to Column

* Lazy `Ago`

* Update styles for faster layouting

* Minor cleanup

* Fix Connection

* Use shadow DOM in `PolkadotIcon`

* Comments and tweaks for the List component

* Faster Tooltip and Truncate

* Minor tweaks

* Tooltiped columns can now be copied

* Future-proof Connection

* Remove the <div> wrapper from Icon

* Fix dash on missing graph data

* Clean up some SVGs

* Cleanup and comments

* Localize the use of `previousKeys` to `recalculateKeys`

* Custom appState disjoint from React component state

* Make appState and appUpdate refs readonly

* Cleanup

frontend/src/components/Truncate.tsx

@@ -0,0 +1,32 @@
+import * as React from 'react';
+
+export namespace Truncate {
+  export interface Props {
+    text: string;
+    chars?: number;
+  }
+}
+
+export class Truncate extends React.Component<Truncate.Props, {}> {
+  public shouldComponentUpdate(nextProps: Truncate.Props): boolean {
+    return this.props.text !== nextProps.text;
+  }
+
+  public render() {
+    const { text, chars } = this.props;
+
+    if (!text) {
+      return '-';
+    }
+
+    if (chars != null && text.length <= chars) {
+      return text;
+    }
+
+    return chars ? (
+      `${text.substr(0, chars - 1)}…`
+    ) : (
+      <div className="Column-truncate">{text}</div>
+    );
+  }
+}