BUG: Get the correct number of planes in the ImageDisplayControls.

When the ImageTubesWidget is initialized it set the number of planes found in
the widget.  The ImageDisplayControlsWidget must be to retrieve the signal
sent.
Merge pull request #249 from thewtex/number-of-planes

BUG: Get the correct number of planes in the ImageDisplayControls.
ENH: Couple the ImageDisplayLogic between tuner's.

We can manipulate all planes simultaneously.
Merge pull request #250 from thewtex/shared-image-display-logic

ENH: Couple the ImageDisplayLogic between tuner's.