+ Target.{hh,cc} class now has a method returning the target material
   + VEventGenerator.{hh,cc} class now returns the effective thickness
     of target seen by the beam before interaction (method CalculateBeamInteraction)
   + Propagate these changes in the different EvenGenerators

* Update Gaspard documentation

   + finish the NPSimulation part of the documentation

	- Wrong detector name was given, problem fixed

* Setting a hi-cup on secondaries
	- There is no more secondaries generated (especially e- in the cryo target)

* Fixing comment in some detector

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   - the output is now on a single line

* Add some documentation for Gaspard (not yet finished)

  directly from the namespace of each class.

* Documentation file (empty for the moment) for the Gaspard project is 
  added

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