ENH: simplify turbulentDigitalFilterInlet BC

tutorials/verificationAndValidation/turbulentInflow/PCF/README

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+#------------------------------------------------------------------------------
+
+The following three synthetic turbulence inflow boundary conditions are
+examined through a single-cell-domain smooth-wall plane channel flow setup:
+
+- turbulentDFSEMInlet (DFSEM)
+- turbulentDigitalFilterInlet (DFM)
+- turbulentDigitalFilterInlet with the forward-stepwise method (FSM)
+
+The input statistics are obtained from:
+
+    Moser, R. D., Kim, J., & Mansour, N. N. (1999).
+    Direct numerical simulation of turbulent channel flow up to Reτ=590.
+    Physics of fluids, 11(4), 943-945.
+    DOI:10.1063/1.869966
+
+from which the input first-/second-order turbulence statistics data for the
+smooth-wall plane channel flow at ReTau=395 were used.
+
+The data is available online from (Retrieved: 21-06-2019):
+
+    https://turbulence.oden.utexas.edu/data/MKM/chan395/
+
+Executing:
+
+./Allrun
+
+The script will run the test case, and collect the plots and samples into
+the 'results' directory.
+
+
+#------------------------------------------------------------------------------