* IcyCanvas: automatically enable all LUT channel when position C
is set to -1 (all channels).
* VtkCanvas:
 - added bounding box, rules, axis display.
 - better update of VTK objects (safe).
 - many improvements, bug fixes and cleanup.
* VtkImageVolume: many improvements and bug fixes.
* VtkUtil: new methods to create volume image and colormap.
* minor change to get rid of the weird IncompatibleClassChangeError
which can happen on some OSX distribution.
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