A tool to handle MOM6_input

[minghangli-uni]

The existing MOM6 input parser cannot correctly parse some parameters because it applies f90nml, which will treat the input as case insensitive, see #14 and #13.

This issue suggests another way for handling MOM6 input files. The tool will be able to read, parse, and modify a MOM input file, and write the modified data to a new file.