First commit of branch performance:

Bugs fixed:
- Solved an issue with particles being injected with infinite velocity
  resulting in Inf velocity in some cells of the output files.
- Particles are now equally distributed in cylindrical geometry along
  the radial direction.

New features:
- Particles now have their own weight that is recalculated when the
  particle moves to a new cell. This avoid the reduction of density at
  r = 0.

Cases:
- Added a case of Argon flow around a cylinder to measure performance
  and future improvements.

src/modules/moduleMesh.f95

@@ -124,11 +124,12 @@ MODULE moduleMesh
 
     END SUBROUTINE collision_interface
 
-    SUBROUTINE findCell_interface(self, part)
+    SUBROUTINE findCell_interface(self, part, oldCell)
       USE moduleSpecies
       
       IMPORT:: meshVol
       CLASS(meshVol), INTENT(in):: self
+      CLASS(meshVol), OPTIONAL, INTENT(in):: oldCell
       CLASS(particle), INTENT(inout):: part
 
     END SUBROUTINE findCell_interface