code: function addonsManager_getAddonButton(aSpec) {
      var spec = aSpec || { };
      var addon = spec.addon;
      var button = spec.button;
  
      if (!button)
        throw new Error(arguments.callee.name + ": Button not specified.");
  
      return this.getAddonChildElement({addon: addon, type: button + "Button"});
    }
docs: Returns the element of the specified add-ons button
  
  @param {object} aSpec
  Information on which add-on to operate on
  Elements: addon  - Add-on element
  button - Button (disable, enable, preferences, remove)
  
  @returns Add-on button
  @type {ElemBase}