Wwise: add port groups

[dromer]

As described in a use-case in the Audiokinetic blog: https://blog.audiokinetic.com/en/sound-in-the-silence-of-space-the-systems-of-hardspace-shipbreaker/ under Heavy Gotchas.

Here they setup a multi-channel/surround config, where by default the c2wwise generator only supports stereo: https://github.com/Wasted-Audio/hvcc/blob/develop/hvcc/generators/c2wwise/c2wwise.py#L77-L82

Likely we should go a similar route as the DPF wrapper and its meta.json for port groups. So this means adding the meta config and adjusting the templates to allow for extending the channel i/o setup.