Clean Plot grid code and add to documentation

docs/api_Mesh.rst

@@ -21,7 +21,24 @@ Each mesh code follows the guiding principles that are present in this
 tutorial, but the details, advantages and disadvantages differ between
 the implementations.
 
+.. plot::
 
+    from SimPEG import Mesh, Utils, np
+    import matplotlib.pyplot as plt
+    sz = [10,10]
+    tM = Mesh.TensorMesh(sz)
+    qM = Mesh.TreeMesh(sz)
+    qM.refine(lambda X: 1 if np.sqrt(((X-0.5)**2).sum()) < 0.3 else 0)
+    rM = Mesh.LogicallyRectMesh(Utils.meshutils.exampleLrmGrid(sz,'rotate'))
+
+    fig, axes = plt.subplots(1,3,figsize=(14,5))
+    opts = {}
+    tM.plotGrid(ax=axes[0], **opts)
+    axes[0].set_title('TensorMesh')
+    qM.plotGrid(ax=axes[1], **opts)
+    axes[1].set_title('TreeMesh')
+    rM.plotGrid(ax=axes[2], **opts)
+    axes[2].set_title('LogicallyRectMesh')
 
 
 Variable Locations and Terminology