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/moduleList.f90

@@ -71,6 +71,7 @@ MODULE moduleList
       DO n=1, self%amount
         !Point element in array to element in list
         partArray(n)%part => tempNode%part
+
         !Go to next element
         tempNode => tempNode%next