Refactoring of the whole superProject.

Since I was stuck on CI because of the ssh things, And still having the comments of Brian in my head i decided to make a little of refactoring in the superproject, especially try to pooling things the maximum.

I also added some features and removed the ones useless in my opinion. A bunch of option never used, and another bunch of cmake macros which i was not able to determine the usefulness. Hope things will be easier to understand and maintain after that.

Of course it will probably have  some regression on other platforms than Linux. If you test it, please let me know.

One last thing, a bad news and a good one.
* It is  compatible neither with visages-superproject and i guess neither with asclepios-superproject.
* It should be very easy to fix that.



#New features : 
* ability to change the setup of all subproject prefix by using CMAKE_PREFIX_INSTALL

* ability to compile the project in static e, the-fPIC flag is automatically enabled on UNIX  with amd64 architecture.

* problem of double DCMTK Linux installation solved.

* semi-automatic activation of  NVCONTROL in VTK  if nvidia GPU is detected, so far only Linux. The option is off by default I do not know if this is something we realy want because of the packaging.

* we dont need to create dummy project just to solve dependencies between external-projects anymore.