Added support for HTML5 drag & drop, more accurate events for jQuery drag & drop

This release features big changes for drag and drop support: FuncUnit will now issue drag events after the initial mousedown/pointerdown event for any elements with the HTML5 "draggable" attribute enabled, per the w3c standard. FuncUnit will also issue the full range of Drag events ensuring that event generation accuracy is very close to full user-emulation.

We have also significantly increased the accuracy of event generation for jQuery drag and drop, sending almost the full range of events that a user would. (We don't send MouseOut / PointerOut because of some variability of when that event should be generated, but this is something we can look into for the future).

Any non-HTML5 drag and drop will default to the jQuery style of event generation automatically. So if you're using a framework that doesn't use jQuery, but drag and drop is triggered by similar events, you will receive upgraded event generation for that too automatically.

If there are any questions or problems, please let me know in Gitter. Thanks!