Re #10804. Added the doc page.

Code/Mantid/docs/source/algorithms/EvaluateMDFunction-v1.rst

+.. algorithm::
+
+.. summary::
+
+.. alias::
+
+.. properties::
+
+Description
+-----------
+
+The algorithm will use the axes of the input workspace to evaluate a functions on them 
+and store the result in the output workspace.
+
+This is a plot of the evaluated function from the usage example below.
+
+.. figure:: /images/Function3D.png
+   :alt: Function3D.png
+
+
+Usage
+-----
+
+.. testcode::
+
+    # Create an empty 3D histo workspace.
+    n = 50 * 50 * 50
+    ws=CreateMDHistoWorkspace(Dimensionality=3, Extents='-1,1,-1,1, -1,1',\
+        SignalInput = [0.0] * n, ErrorInput = [1.0] * n,\
+        NumberOfBins='50,50,50',Names='Dim1,Dim2,Dim3',Units='MomentumTransfer,MomentumTransfer,MomentumTransfer')
+
+    # Define a function
+    function = 'name=UserFunctionMD,Formula=1.0/(1.0 + 100*(0.5 - x^2 - y^2 -z^2)^2)'
+
+    # Evaluate the function on the created workspace
+    out = EvaluateMDFunction(ws,function)
+
+    # Check the result workspace
+    print out.getNumDims()
+    print out.getXDimension().getName()
+    print out.getYDimension().getName()
+    print out.getZDimension().getName()
+    
+    
+Output
+######
+
+.. testoutput::
+
+  3
+  Dim1
+  Dim2
+  Dim3
+
+.. categories::