refactor ui initialization each group in a function, new document dialog, fix parallax camera and drawing order clipping problem

engine/app.h

@@ -88,4 +88,15 @@ public:
     bool key_down(kKey key);
     bool key_up(kKey key);
     bool key_char(char key);
+
+    void init_toolbar_main();
+    void init_toolbar_draw();
+    void init_sidebar();
+    void init_menu_file();
+    void init_menu_edit();
+    void init_menu_layer();
+    void dialog_newdoc();
+    void dialog_save();
+    void dialog_open();
+    void dialog_export();
 };