minor: edit of comment to match notation
I had gotten confused over the units of, and the size of, the hydraulic conductivity constant.  As a result I was working with really low-conductivity hydrology which implied unreasonably high W values (water thicknesses) and very fast run times.  With this commit the code (but not all the test cases) fully match the Schoof et al [2012] and Hewitt et al [2012] conventions.  The examples/nbreen/run.sh script and its override parameters in examples/nbreen/nbreen_config.cdl also match the Schoof/Hewitt work.  The model results for Nbreen then seem very reasonable relative the Schoof/Hewitt work.  (The results are more expensive computationally, but also more interesting physically!  The documentation in the private hydrolakes/ repo has not been fully updated to match yet.)  The Test P example cannot be used until it is inspected and updated; I think all we need to do is shorten the run.