Escher: Adding Window, ViewController and TabViewController

Change-Id: I6a13fe95e846cfcc43f783e8b4d88ea4ad9ee585

escher/src/view_controller.cpp

@@ -0,0 +1,12 @@
+#include <escher/view_controller.h>
+
+ViewController::ViewController() {
+}
+
+char * ViewController::title() {
+  return nullptr;
+}
+
+void ViewController::handleKeyEvent(int key) {
+  // Do nothing
+}