Support Command aliases (eg. shortnames) - #185

$ ./bin/user --help
Usage: ./bin/user <command> [options] [operands]

Options:
  --version      Show version information and quit
  -?, --help     Show this help and quit
  -v, --verbose  Increase verbosity

Commands:
  register  Register a user [alias: reg, init]
  password  Set or reset a users password [alias: passwd, pw]
  list      List users [alias: l, ls]


$ ./bin/user list
[... list command output]

$ ./bin/user ls
[... list command output]