PortSpec is the specification of a port or port range
NewPortSpec creates a new port spec
NewPortSpecFromString creates a new port spec
IsIncluded returns trues if a port is within the range of the portspec
IsMultiPort returns true if the spec is for multiple ports.
Overlaps returns true if the provided port spect overlaps with the given one.
Range returns the range of a spec.
SinglePort returns the port of a non multi-port spec
MultiPort returns the multi-port range as a string.
Value returns the value of the portspec if one is there