use more verbose output type for unittests on travis
refactored logic from init_users() into mch_get_usernames()
moved mch_get_user_name() and mch_get_uname() into os/users.c
removed get_user_name() and replaced calls with mch_get_user_name()
refactored part of expand_env_esc() into mch_get_user_directory()