Merge branch 'feature/collisionPairs' into feature/electromagnetic

Merging branches and fixing a number of important issues:

- Initial particles were not being assigned to the list of particles.

- List of particles was being erased every iteration, even if species
  was not pushed.

These caused issues with the calculation of collisions when a species
was frozen.

Now, things should work properly. All particles are properly added to
the volume list and the list is erased ONLY if the species has been
updated.

I hope that collisions are now properly accounted for per species pair.

src/modules/mesh/2DCyl/moduleMesh2DCyl.f90

@@ -299,6 +299,9 @@ MODULE moduleMesh2DCyl
 
       CALL OMP_INIT_LOCK(self%lock)
 
+      ALLOCATE(self%listPart_in(1:nSpecies))
+      ALLOCATE(self%totalWeight(1:nSpecies))
+
     END SUBROUTINE initVolQuad2DCyl
 
     !Computes element area
@@ -659,6 +662,9 @@ MODULE moduleMesh2DCyl
 
       CALL OMP_INIT_LOCK(self%lock)
 
+      ALLOCATE(self%listPart_in(1:nSpecies))
+      ALLOCATE(self%totalWeight(1:nSpecies))
+
     END SUBROUTINE initVolTria2DCyl
 
     !Random position in quadrilateral volume