Final implementation of ionization process by electron impact.

Possibility to input initial species distributions (density, velocity
    and temperature) via an input file for each species.

New moduleRandom includes function to generate random numbers in
different ways (still uses) the implicit RANDOM_NUMBER().

src/modules/mesh/1DCart/moduleMesh1DCartBoundary.f90

@@ -66,25 +66,16 @@ SUBMODULE (moduleMesh1DCart) moduleMesh1DCartBoundary
     SUBROUTINE wallTemperature(edge, part)
       USE moduleSpecies
       USE moduleBoundary
-      USE moduleConstParam, ONLY: PI
+      USE moduleRandom
       IMPLICIT NONE
 
       CLASS(meshEdge), INTENT(inout):: edge
       CLASS(particle), INTENT(inout):: part
-      REAL(8):: x, y
 
       !Modifies particle velocity according to wall temperature
       SELECT TYPE(bound => edge%boundary%bTypes(part%sp)%obj)
       TYPE IS(boundaryWallTemperature)
-        x = 0.D0
-        DO WHILE (x == 0.D0)
-          CALL RANDOM_NUMBER(x)
-
-        END DO
-
-        CALL RANDOM_NUMBER(y)
-
-        part%v(1) = part%v(1) + bound%vTh*DSQRT(-2.D0*DLOG(x))*DCOS(2.D0*PI*y)
+        part%v(1) = part%v(1) + bound%vTh*randomMaxwellian()
 
       END SELECT