md_trim.pl -- Code list whitespace trimming

Helper module to trim whitespaces from lists of codes.

trim_left(+Codes, -Result) is det
Trims whitespaces from the beginning of the list of codes.
trim_right(+Codes, -Result) is det
Trims whitespace from the end of the list of codes.
trim(+Codes, -Result) is det
Trims whitespace from both sides of the list of codes.