title: Change all file icons with same type [Yosemite]
body: <p>I have many excel files in my computer, and the icon of all of them are plain paper, like this:
  <img src="https://i.stack.imgur.com/cvV0f.png" alt="enter image description here"></p>
  
  <p>I want all icons to be .numbers icon. Do anyone know how to do that ?</p>