First commit of code.

New functionality:
- DSMC module:
  - 2D cyl geometry
    - GMSH file format
    - Elastic cross-section for Argon-Argon collisions.
    - Basic boundary conditions: reflection, absorption and axis
      symmetry.

Bugs fixed:

Other comments:
- Still searching for name.

src/modules/moduleRefParam.f95

@@ -0,0 +1,10 @@
+!Reference parameters
+MODULE moduleRefParam
+  USE moduleConstParam
+  !Parameters that define the problem (inputs)
+  REAL(8):: n_ref, m_ref, T_ref, r_ref, sigma_ref!, q_ref=1.6022D-19
+  !Reference parameters for non-dimensional problem
+  REAL(8):: L_ref, v_ref, ti_ref, Vol_ref
+
+END MODULE moduleRefParam
+