Need for sending custom data on dragOver, dragLeave and dragEnter events

Adds options for using callback functions on dragOver, dragLeave and dragEnter events - similar to ui-on-drop and on-drop-success callbacks. This gives the possibilty of using onDrag(Over/Leave/Enter)Handler and passing additional paramters to the handler (not possible when using ANGULAR_HOVER event). This is very helpful when building a sortable list of elements that shows preview of final order while still dragging.

Further more adjusted parameter of ANGULAR_DRAG_START event broadcast from JSON string to dragData object (feels a bit cleaner ;)

Hope you like! If you have questions, get in touch.

Cheers
Henry