Update issue #100 : Allow connection between connected pins by dragging.
Any connected pins are first disconnected before connection is attempted
If disconnection fails the new connection is not attempted
If the new connection fails any disconnected pins remain disconnected
Still need to add a visual cue for when a new connection will cause existing connections to be disconnected


git-svn-id: http://graph-studio-next.googlecode.com/svn/trunk@115 c2f33eb2-41b2-391d-4cb4-d9d0608729ba