fix(draggable): namespace events with unique ids

Until now if you had multiple instances of Draggable in the same page,
when destroying one of them, all of the events binded to other
instances were also destroyed.

So, we are namespacing event names with unique id’s per instance to ensure
only that only the corresponding events are unbinded.

The other solution is to cache references to the event handlers, but most
of them are proxied or throttled which makes more mess...
Release v0.5.6