Toggle Synchronization of minion-list on/off

* We still need to sort the list. Is this the job of the "array" formatter ?

* CSS note: ideally I would love just one button with a little green light (no text, just a tip). [Something like this](http://tympanus.net/Tutorials/CSS3ButtonSwitches/index.html) but with only one button.

* not tested in IE because xhr.js does not work in IE9