New Examples

- Put all examples in same directory
   - Make a single test
   - use __init__.py to create the docs automatically

SimPEG/Examples/Mesh_QuadTree_HangingNodes.py

@@ -0,0 +1,32 @@
+from SimPEG import *
+
+def run(plotIt=True):
+    """
+        Mesh: QuadTree: Hanging Nodes
+        =============================
+
+        You can give the refine method a function, which is evaluated on every cell
+        of the TreeMesh.
+
+        Occasionally it is useful to initially refine to a constant level
+        (e.g. 3 in this 32x32 mesh). This means the function is first evaluated
+        on an 8x8 mesh (2^3).
+
+    """
+    M = Mesh.TreeMesh([8,8])
+    def function(cell):
+        xyz = cell.center
+        dist = ((xyz - [0.25,0.25])**2).sum()**0.5
+        if dist < 0.25:
+            return 3
+        return 2
+    M.refine(function);
+    M.number()
+    if plotIt:
+        import matplotlib.pyplot as plt
+        M.plotGrid(nodes=True, cells=True, facesX=True)
+        plt.legend(('Grid', 'Cell Centers', 'Nodes', 'Hanging Nodes', 'X faces', 'Hanging X faces'))
+        plt.show()
+
+if __name__ == '__main__':
+    run()