BUG: get Xdmf reader to work correctly in PV using the new pipeline; changing which arrays to read is correctly propagated to the GUI
BUG: get Xdmf reader to work correctly in PV using the new pipeline; changing which arrays to read is correctly propagated to the GUI

cjh1/Xdmf2,cjh1/Xdmf2,cjh1/Xdmf2