Rubber band zoom + slice change via keyboard

This pull request adds the following features:
- A rubber band zoom feature can be activated when the mouse interaction is set to Zoom via ctrl + click. (drag to create a rectangular area to zoom in)
- KeyEvents are now received by the qvtkWidget which able us to interact with the view via the keyboard. For now the up and down key offers an easy and precise way to travel through the slices of an image.
Several key shortcuts were already defined in the code of vtkinria, most of them are now desactivated. I advise the reviewers to reactivate them and test them so that we can discuss on their usefulness for the software. 
Here are the lines that I commented :  
vtkInteractorStyleImageView2D.cxx line 458-462
vtkImageViewCollection.cxx line 404-423
vtkImageView2DCommand.cxx line 159-168
In the file vtkImageView2D cxx, I setted the shortcut to the distanceWidget to off.
We also have an interesting widget called anglewidget with which we can measure angles, the shortcut is still on (key 'o')

- The shortcut (CTRL+SHIFT+L) to generate an histogram of an image (medClutEditor) did not work anymore, therefore I modifed it to CTRL + L

The rubber band zoom might presents some bugs with the pad of a laptop if not used correctly.

https://med.inria.fr/redmine/issues/1747
Reviewers = Olivier , Loic
Merger = Olivier