this commit is related to the medMaskApplication plugin
This commit brings severals improvements to the varSeg plugin :
- The possibility to apply the current segmentation to the image
- a start button that activates the segmentation mode
- a cross cursor when the segmentation is activated
- a Abandon button which brings back the original image
- after clicking on the start button, the currentView variable wont be
  changed, this choice should prevent bugs if several images are opened
There are still several bugs :
- focus loss (works only in windowing mode)
- windowing setted to 0/1 when the data is setted (see applyMask or
  Abandon)
- removing landmarks from 2d view does not work
- binary image generated does not look that good (borders, ...)