fleetctl: Add restart and ssh-port functionality

Starts and stops a unit in one command.
Adds support to specify SSH port for SSH based commands:
* journal
* status
* ssh
* restart

refs #760
refs #932 
Per https://code.google.com/p/go-wiki/wiki/CodeReviewComments#Initialisms, "Ssh" should always be written with a consistent case: "SSH" or "ssh" depending on the context.