--addr -> multiple -H + unix

mimic docker flags, `swarm manage` now take multiple `-H` flags instead of `--addr`

Theses hosts can contains a protocol like:

`unix://swarm.sock`
`tcp://ip:port`
`ip:port` (default to `tcp`)

As `swarm` doesn't need to be stared as root, the socket is created as your current user and has rights `660`
Perhaps add a comment explaining the umask + chmod trick?

Otherwise looks good.