Carousel tile with cycle2

Hi, I'd like some good thoughts on this, though I should first mention outstanding items (which should be implemented next week) are:
   * Swipe gesture - (Cycle2 needs "jQuery Mobile" to get this working - is this included in the dependencies somewhere?)
   * Correct template to use all configured fields (as in list.pt)

That aside, I'd particularly like thoughts on:
* whether switching between galleria & cycle2 themes could be simpler
* whether doc amendments are in the right place & say too little or too much
* if test fixture set up in testing.py is a good way to do this
* should Cycle2 view look (as currently) fairly close to galleria view, or be distinct

Or anything else...

closes #442 

we probably want to use a browser layer from [collective.js.galleria](https://github.com/collective/collective.js.galleria/blob/master/collective/js/galleria/profiles/default/browserlayer.xml)