Fix  #21

Don't include label height for element size calculation if the element
has no name.
This fixed the problem that premature picking elements when moving the
mouse from below.
(Also integrated latest changes to D2dCircuitRenderer)
Improved estimation for empty-content node height

This address the issue that when a node only has one input/output pin
but no image, the line separating the title and content is still draw
(#19)
Added support to drag/drop on to a group #23

Circuit Editor added support to drag/drop on to a group #23
Merge pull request #1 from SonyWWS/master

Update from original