New method: upload(dirnum/code).

Added support for dirnum parameter (optionally instead of internal code) to
various file-xfer related methods.
Renamed many methods to follow the verb_noun naming convention:
list_users, edit_user, list_logons, read_mail, list_files, list_file_info,
post_msg, cfg_msg_scan, cfg_msg_ptrs, reinit_msg_ptrs, and list_nodes.