Added test for suport for sti-file input for used Piping models. Made some small improvements the testdata to get some real results. Checked these results by hand to ensure correctness.Related to Issue [MWDAM-1677]
Corrected failing test involving Piping Bligh and SellmeijerVnk model. Made sure results for timeseries are initialized as NaN.Related to Issue [MWDAM-1677]