Allow unknown flags

[jeffque]

Check #23

If there is a not previously treated CLI flag, one should not forbid user to inform it.

Could be used to bypass a known flag, if for some reason the Ouroborus::Container implementation is not proper.

CLI flags must always start with a - or --. It can has a complement, it should be informed together with the flag. Complement can be a single value, or a list. If complement is a list, then it shall be reduced as a comma separated string.

Passing a flag that does not need a complement:

def createContainer
  # creates a new valid Ouroborus::Container instance
end

container = craeteContainer
container.addDockerFlag "--rm"
container.addDockerFlag "--dns", "8.8.8.8", "8.8.4.4"