* General improvements and better support for BooleanMask3D/4D/5D
classes.
* ROI:
  - added default 5D point constructor.
  - added ROI.hasSelectedPoint() method (used for cursor update in
canvas)
  - added ROI.getBooleanMask2D(..) method
  - added boolean and subtraction operations support.
* ROI2D: code cleanup and refactoring.
* ROI2DArea: code cleanup and new methods to set individuals points.
* ROI3D/4D/5D: better BooleanMask support.
* ROI3DStack: many improvements, should be usable now.
* ROI3DArea: basic implementation.
* ROIUtil: added boolean and subtraction operations for ROI list.
* Improved Point3D/4D/5D classes.
* Improved Rectangle3D/4D/5D classes.
* IcyCanvas: minors changes and refactoring.
* Canvas2D: support for future 3D/4D/5D ROI drawing
* Overlay: events now support 5D coordinates
* PluginROI interface modified, plugins using it have to be updated !
* some refactoring.
* fixed some backward compatibility issues.