Added LoadingScreen for full-size loading placeholder

rpdata-ui/src/common/LoadingScreen.js

@@ -0,0 +1,13 @@
+import React, { Component } from 'react';
+import Background from "./Background";
+
+import './css/LoadingScreen.css';
+
+export function LoadingScreen({className}) {
+  return (
+    <div className={`Loading ${className}`}>
+      <Background />
+      <div className="text color-primary">Loading...</div>
+    </div>
+  )
+}

rpdata-ui/src/common/css/LoadingScreen.css

@@ -0,0 +1,7 @@
+.Loading .text {
+  width: 100%;
+  margin-top: 6em;
+  font-size: 3em;
+  opacity: 0.5;
+  text-align: center;
+}