New medViewPropertiesToolBox

Here is the work in progress for the new medViewPropertiesToolbox (this PR is based on PR#90 ).

I created the medParameters and started using them in the v3dView interactors (you should be able to test the image,  mesh and tensor interactors ). This way, all the interactor's toolboxes could be removed in the end.

From the the new toolbox, you can now select several views/layers and apply properties simultaneously to them.
I've tried to synchronise the view selection (from the toolbox or by clicking in the view) but this is still in progress. (I've also allowed CTRL+click in the views).

At least, what's left to be done (if you're okay with what's in there of course ;) ):
 - finish the interactors
 - synchronize the views selection between the toolbox and the containers
 - link the visibilty and opacity properties
 - change the behaviour for the link position and link window level.

Thanks for your comments and if someone wants to take this over while I'm away, feel free!

Guillaume