MERRA2 double-sided dynamic lapse rate cutoff

[Kristen-M-Whitney]

Option to apply a double-sided cutoff to the MERRA-2 dynamic lapse rate values.

If using MERRA-2 with dynamic lapse rates turned on, then users can specify the following options in the config file:

• apply a double-sided cutoff - if not present, no cutoff is applied
• specify a maximum lapse rate cutoff value (K/m) - if not present, the default is 0.01 K/m
• specify a minimum lapse rate cutoff value (K/m) - if not present, the default is -0.01 K/m

Note that @dmocko and @sujayvkumar have helped with this enhancement.