GUAC-975: Only display views once critical data is loaded.

guacamole/src/main/webapp/app/index/styles/loading.css

@@ -25,6 +25,14 @@
     min-height: 200px;
 }
 
+.view.loading {
+    position: fixed;
+    top: 0;
+    left: 0;
+    width: 100%;
+    height: 100%;
+}
+
 .loading * {
     visibility: hidden;
 }