Structure for 3D Cartesian Grid created.

Unification of boundary conditions into one file.

Some changes to input file for reference cases. This should have been
done in another branch but I wanto to commit to save progress and I
don't want to deal with tswitching branches right now, I'm very busy
watching Futurama.

runs/1D_Cathode/mesh.geo

@@ -0,0 +1,16 @@
+Lcell = 0.00005;
+
+x0 = 0.001;
+xf = x0 + 100.0*Lcell;
+
+Point(1) = {x0, 0, 0, 1};
+Point(2) = {xf, 0, 0, 1};
+
+Line(1) = {1, 2};
+
+Physical Point(1) = {1};
+Physical Point(2) = {2};
+
+Physical Line(1) = {1};
+
+Transfinite Line {1} = (xf-x0)/Lcell + 1 Using Progression 1;