Create a postprocessor for complete material output.

This is a proposed postprocessor for the complete output of the evaluate function of the material model. We are currently working with a material model that is very slow / complicated and I was annoyed by the waste of time to call the evaluate function for every material property output, although they are all evaluated in the same function. There would be other ways to achieve this, but they would all include larger changes in the material model interface (e.g telling the evaluate function what property is asked for) and we would always have the overhead of setting up an material_model_inputs and _outputs for just one returned quantity. Let me know what you think about it, and I could adjust it.
Maybe state the purpose of the viz postprocessor here, as in "There are a number of other visualization postprocessors that offer to write individual material properties. However, they all individually have to evaluate the material model. This is inefficient if one wants to output more than just one or two of the fields provided by the material model. The current postprocessor allows to output a (potentially large) subsets of all of the information provided by material models at once, with just a single material model evaluation per output point." Or some such.