add warning/exit for undefine/obsolete selectivity patterns

[k-doering-NOAA]

Apparently, if pattern 30 is chosen for length selectivity, the model will run sometimes: example,even though according to the manual pattern 30 should no longer be used

An explicit exit should be added to Stock Synthesis (and r4ss read function to prevent this)

@Rick-Methot-NOAA , I can work on this if you think it is a good idea.

[Rick-Methot-NOAA]

concur. Please add a warning with recommendation on which better pattern to use. Make it a warning with exit.