Issue with random position in volumes

Fixed an issue in which  the position in triangular an thetrahedron
elements were not correctly being computed.

Other minor issues fixed:
  - Units in input file now do not use '/'.
  - Collisions accuratly conserve momentum.
  - Minor improvements in mass calculation in collisions.

src/modules/mesh/moduleMesh.f90

@@ -186,15 +186,6 @@ MODULE moduleMesh
 
     END SUBROUTINE initVol_interface
 
-    SUBROUTINE scatter_interface(self, part)
-      USE moduleSpecies
-      
-      IMPORT:: meshVol
-      CLASS(meshVol), INTENT(in):: self
-      CLASS(particle), INTENT(in):: part
-
-    END SUBROUTINE scatter_interface
-
     PURE FUNCTION gatherEF_interface(self, xi) RESULT(EF)
       IMPORT:: meshVol
       CLASS(meshVol), INTENT(in):: self
@@ -574,6 +565,7 @@ MODULE moduleMesh
 
     !TODO: try to combine this with the findCell for a regular mesh
     !Find the volume in which particle reside in the mesh for collisions
+    !No boundary interaction taken into account
     SUBROUTINE findCellCollMesh(part)
       USE moduleSpecies
       IMPLICIT NONE
@@ -669,7 +661,7 @@ MODULE moduleMesh
       DO e=1, self%numVols
         vol => self%vols(e)%obj
         nPart = vol%listPart_in%amount
-        !Computes iterations if there is more than one particle in the cell
+        !Calculates number of collisions if there is more than one particle in the cell
         IF (nPart > 1) THEN
           !Probability of collision
           pMax = vol%totalWeight*vol%sigmaVrelMax*tauMin/vol%volume