Instrument hovering over the install button

[muffinresearch]

Relates to #1107

This one is a bit counter-intuative since it relates clicks to when the user hovers but that's what the requirements ask for.

ga('ec:addProduct', {                      // Provide product details in an impressionFieldObject.
  'id': '123',                             // id of the add-on
  'name': 'Golden butterfly_9',            // name of the add-on - <add-on name>
  'category': 'themes',                    // category the add-on belongs to
  'brand': 'atalaia-1364594162.97',        // developer name
  'position': 1,                           // add-on position on about:addons page
});

ga('ec:setAction', 'click');

ga('send', 'event', 'Add-ons Interactions', 'hover', '<add-on name>');