SCENARIO:
I have two types of Sortables that share Draggables (by containment):
(1) a "groupDrop" can contain only Draggable "field" elements.
(2) a "zone" can contain Draggable "field" elements and/or Draggable "group" elements.
A Sortable "groupDrop" is always within a Draggable "group".
Each "groupDrop" has option only:"field" to prevent one group from being dropped within another.
PROBLEM:
If a "group" is dragged from a "zone" and dropped in a "groupDrop", the groupDrop correctly does not invoke the onUpdate function. However, the group incorrectly drops in the groupDrop, and the zone onUpdate function is invoked (and missing the dragged group).
If a "groupDrop" is set to only accept a "field", then any attempt to drop a "group" in it should fail completely. The "group" should revert back to its original position.
