Support for port forwarding rules

[pmarko1711]

I would wish to use the library to be activate and deactivate port forwarding rules remotely (in fact, over telegram) for a short period of time. Port forwarding commands are however not supported for now.

I'm happy to try adding it myself, but not sure how to deal with set commands (not yet familiar with asyncio).

As for the comments, looking at compal_CH7465LG_py I believe it is 121 to get the forwarding rules, and 122 to set a port forwarding rule.

EDIT:
actually, what I would want to set/get are filter rules (111/112 for ipv6, 109/110 for ipv4)

[krzysztof-kwitt]

@fabaff is it done?