Allow to ignore several ports

[frsantos]

The -ignoreport option permits only one port to be ignored. It could be useful to ignore a list of ports.

[mfrister]

Yep, that would be nice. We don't need it right now, so feel free to create a pull request.

[martinseener]

@frsantos any updates on this one? We will close this issue if there is no further interest in it.