Set and parse a password file, setting username and password as specified in the file.
A password file is a ASCII text file, with username and passwords pairs on each line, seperated [delimited] by a semicolon. Lines starting with a hash [#] are comments. If only one non-commented line is present in the file, that username and password will be used for authentication. If more than one set of usernames and passwords are present, the username must be specified, and the matching password from the file will be used.
# Example password file.
fredfs@example.com:Wilma4evah
barney@example.net:B3ttyRawks