Changes to 1D Cathode example

Now it is uses the text mesh format.
All output files are now included as they are simple csv files easy to
understand.

runs/1D_Cathode/mesh.py

@@ -0,0 +1,18 @@
+import numpy as np
+import csv
+
+x0 = 0.0
+Dx = 4.0e-5
+xF = x0 + 50.0*Dx
+
+x = np.arange(x0,xF + Dx,Dx)
+p = np.zeros_like(x)
+p[ 0] = 1
+p[-1] = 2
+p = np.int32(p)
+
+with open('mesh.csv', 'w') as csvfile:
+    csvwriter = csv.writer(csvfile)
+    csvwriter.writerow(['Position(m)','Physical ID'])
+    for x_i, p_i in zip(x, p):
+        csvwriter.writerow([x_i,p_i])