Fixes, Android adaptive icon for crypto.

lib/base/base_state.dart

@@ -50,6 +50,8 @@ abstract class BaseState<T extends StatefulWidget> extends State<T> {
   /// Возвращает контейнер с всеми виджетами экрана.
   Widget getScreenContent();
 
+  bool isAutomaticallyImplyLeading();
+
   /// Возвращает заголовок для AppBar
   String getTitle() {
     return null;
@@ -59,6 +61,7 @@ abstract class BaseState<T extends StatefulWidget> extends State<T> {
     return new AppBar(title: new Container(
         margin: new EdgeInsets.only(left: 16.0),
         child: new Text(getTitle(), style: new TextStyle(fontSize: 18.0))),
+        automaticallyImplyLeading: isAutomaticallyImplyLeading(),
         backgroundColor: Resources.getPrimaryColor(app),  actions: getMenuButtons());
   }