Add documentation to explain the use of _m notation to identify a member of a class

[Bai-Li-NOAA]

We should include documentation within the collaborative workflow document explaining the use of "_m" notation to ensure clarity for both users and developers. Please refer to the comment here for more information.

[kellijohnson-NOAA]

The *_m() functions should not be used on the daily, instead they are meant to be accessors used by internal FIMS functions. I noticed that not all of the functions are documented. Their use does not need to be documented in the collaborative workflow guide because once the wrapper function is written it will be clear how to use them for power users.

• The R interface group will make sure that they are all documented using roxygen and before this issue is closed