[NONE] Update "nestedGraph" and "nestingNode" attributes simultaneously.
[438734] Move visualizations into the content parts.

The FXLabeledNode and FXLabeledConnection classes will probably be removed as
they do not contribute enough functionality to justify their existence.
[NONE] Remove hover feedback immediately when no handles are created and the part is un-hovered.
[438734] Fix layout context bounds in the stand-alone example.
[438734] Only send property change notifications when the value actually changes.
[438734] Check that the host is part of the layout-context before trying to provide layout information.
[438734] Do not set "pruned" attribute to "false" when it did not exist in the first place.
[438734] Show icon indicating a node is associated with a nested graph.
[NONE] Add support for cancelling drag policies.

A click policy may alter content that is currently processed by a drag policy.
In this case, the click policy may cancel all running drag policies to avoid
conflicts.
[438734] Add policies to open nested graphs/parent graphs.