am b4d2e42a: docs: revise menu guide to focus more on using menu resources instead of defining menus in code. And revise some style.

Merge commit 'b4d2e42a8508a09f944b13f27c043952eef6c1cc' into gingerbread

* commit 'b4d2e42a8508a09f944b13f27c043952eef6c1cc':
  docs: revise menu guide to focus more on using menu resources