Updating changelog for v2.1.1
VTK thumbnails for Mac crash when doing several (VTK and system related crash), revert to no thumbnails for VTK on Mac
Merge pull request #78 from ocommowi/1745-vtk-thumbnails-mac

VTK thumbnails for Mac crash when doing several thumbnails
Update release notes for 2.1.1
First steps towards rbZoom
-Solves the lost of control of focus over containers
-Improves rbzoom activation
-keyevent from qvtkwidget are sent to medMainWindow enabling the
activation of shortcut via keypressevent and keypressrelease
Small changes
removes useless lines
-Now after choosing zoom as the main mouse interaction the focus is
directly brought back to the view.
- A new shortcut has been defined for the histogram
- This commit desactivates most of the key shortcuts that were existing in
  the code of vtkInria.