Create separate parameter for passing comma-separated list of columns/loci to keep

[apetkau]

Context

Right now, there is one parameter --columns, which can be used to either pass a reference to a file containing a list of columns/loci to use for distance calculations, or which can be a comma-separated string of columns/loci:

--columns COLUMNS Single column file with one column name per line or list of columns comma separate (default: None)

Requested change

This change would be to separate out these two scenarios into two parameters. For example:

• --columns: Used to pass a file containing columns/loci to keep.
• --columns_string: Used to pass a string of columns to keep.