this new command takes a sub-command name as its first positional argument
and passes the rest of arguments to the corresponding sub-module.
for example, 'run' sub-command is an equivalent to bin/ryu-manager.
this commit does not replace the existing commands like ryu-manager.
this merely adds new ways to invoke the functionalities.
Signed-off-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>