add some cube meshes none of which is working

examples/cube/cube_pec.json

@@ -7,7 +7,7 @@
   },
   "Model":
   {
-    "Mesh": "mesh/cube.mesh",
+    "Mesh": "mesh/cube.msh",
     "L0": 1.0e-2,  // cm
     "Refinement":
     {

examples/cube/mesh/cube.geo

@@ -0,0 +1,42 @@
+SetFactory("OpenCASCADE");
+gridsize = 100/3;
+
+// Face
+// -- Points
+Point(1) = {0,0,0,gridsize};
+Point(2) = {0,0,100,gridsize};
+Point(3) = {0,100,100,gridsize};
+Point(4) = {0,100,0,gridsize};
+
+// -- Line
+Line(5) = {1,2};
+Line(6) = {2,3};
+Line(7) = {3,4};
+Line(8) = {4,1};
+Line Loop(9) = {5,6,7,8};
+
+// -- Surface
+Plane Surface(10) = {9};
+Recombine Surface{10};
+
+// Extrude to 3D
+bodyExtrusion[] =
+Extrude { 100,0,0 }
+{
+    Surface{10};
+    Layers{100/gridsize};
+    Recombine;
+};
+
+// Boundaries
+Physical Surface("back") = {10};
+Physical Surface("right") = {bodyExtrusion[2]};
+Physical Surface("top") = {bodyExtrusion[3]};
+Physical Surface("left") = {bodyExtrusion[4]};
+Physical Surface("bottom") = {bodyExtrusion[5]};
+Physical Surface("front") = {bodyExtrusion[0]};
+
+// Volume
+Physical Volume("mesh") = {bodyExtrusion[1]};
+Mesh 3;
+Coherence Mesh;