Not fully conservative but works

The code is still not fully conservative in intra-species collisions
(small error) but at least now is working.

I have to test species with different weight.

I have to implement a fully conservation for intra-species.

src/modules/moduleCoulomb.f90

@@ -59,8 +59,10 @@ MODULE moduleCoulomb
       self%sp_i => species(i)%obj
       self%sp_j => species(j)%obj
 
-      self%one_plus_massRatio_ij = 1.D0 + (self%sp_i%weight*self%sp_i%m)/(self%sp_j%weight*self%sp_j%m)
+      self%one_plus_massRatio_ij = 1.D0 + self%sp_i%m/self%sp_j%m
 
+      Z_i = 0.D0
+      Z_j = 0.D0
       SELECT TYPE(sp => self%sp_i)
       TYPE IS (speciesCharged)
         Z_i = sp%q