add catch multiplier as feature to a model

[k-doering-NOAA]

This feature is not included in the test set. Could add this to the Simple_Lorenzen or some other model rather than creating a new one.

[Rick-Methot-NOAA]

That would work, as would adding it to the, still wished for, mega-tester.
Catch_multiplier will have some interaction with F_method, but is orthogonal to essentially everything else.
This week, I will commit to getting that mega-tester into the git repo so we all can be adding to it.