Most of modules organized

Most of the modules are organized in subfolders.

Maybe some big re-organization is needed in the future, but for now I am
happy.

src/modules/common/moduleRandom.f90

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+MODULE moduleRandom
+  !Interface for random number generator
+  INTERFACE random
+    MODULE PROCEDURE randomReal, randomRealAB, randomIntAB
+
+  END INTERFACE random
+
+  CONTAINS
+    !Returns a Real random number between 0 and 1
+    FUNCTION randomReal() RESULT(rnd)
+      IMPLICIT NONE
+
+      REAL(8):: rnd
+
+      rnd = 0.D0
+      CALL RANDOM_NUMBER(rnd)
+
+    END FUNCTION randomReal
+
+    !Returns a Real random number between a and b
+    FUNCTION randomRealAB(a, b) RESULT(rnd)
+      IMPLICIT NONE
+
+      REAL(8), INTENT(in):: a, b
+      REAL(8):: rnd
+      REAL(8):: rnd01 !random real between 0 and 1
+
+      rnd = 0.D0
+      CALL RANDOM_NUMBER(rnd01)
+
+      rnd = (b - a) * rnd01 + a
+
+    END FUNCTION randomRealAB
+
+    !Returns an Integer random numnber between a and b
+    FUNCTION randomIntAB(a, b) RESULT(rnd)
+      IMPLICIT NONE
+      
+      INTEGER, INTENT(in):: a, b
+      INTEGER:: rnd
+      REAL(8):: rnd01
+
+      rnd = 0.D0
+      CALL RANDOM_NUMBER(rnd01)
+
+      rnd = INT(REAL(b - a) * rnd01) + 1
+
+    END FUNCTION randomIntAB
+
+    !Returns a random number in a Maxwellian distribution of mean 0 and width 1
+    FUNCTION randomMaxwellian() RESULT(rnd)
+      USE moduleConstParam, ONLY: PI
+      IMPLICIT NONE
+
+      REAL(8):: rnd
+      REAL(8):: x, y
+
+      rnd = 0.D0
+      x = 0.D0
+      DO WHILE (x == 0.D0)
+        CALL RANDOM_NUMBER(x)
+      END DO
+      CALL RANDOM_NUMBER(y)
+
+      rnd = DSQRT(-2.D0*DLOG(x))*DCOS(2.D0*PI*y)
+
+    END FUNCTION randomMaxwellian
+
+    !Returns a random number weighted with the cumWeight array
+    FUNCTION randomWeighted(cumWeight, sumWeight) RESULT(rnd)
+      IMPLICIT NONE
+
+      REAL(8), INTENT(in):: cumWeight(1:)
+      REAL(8), INTENT(in):: sumWeight
+      REAL(8):: rnd0b
+      INTEGER:: rnd
+
+      rnd0b = random(0.D0, sumWeight)
+      rnd = MINLOC(DABS(rnd0b - cumWeight), 1)
+
+    END FUNCTION randomWeighted
+
+END MODULE moduleRandom