Container: support flexbox directives.

src/widgets/Container.tsx

@@ -6,12 +6,17 @@ import Paper from "@material-ui/core/Paper";
 
 import "./Container.css";
 
-export default (props: {style?: any, children: any}) => (
+export default (props: {style?: React.CSSProperties, children: any}) => {
-  <div className="Container" style={props.style}>
+  const display = props.style?.display;
-    <Paper elevation={3}>
+  const flexDirection = props.style?.flexDirection;
-      <div className="Container-inner">
+
-        {props.children}
+  return (
-      </div>
+    <div className="Container" style={props.style}>
-    </Paper>
+      <Paper elevation={3} style={{ display, flexDirection, flexGrow: 1 }}>
-  </div>
+        <div className="Container-inner" style={{ display, flexDirection, flexGrow: 1 }}>
-);
+          {props.children}
+        </div>
+      </Paper>
+    </div>
+  );
+};