Add methods to retrieve physical device information (Updated)

[Supernovatux]

Based on #17 by @dhduvall. It was very hard to rebase the 7 year old PR. So I created a new one here. Borrows most of the code from the old one.

Additions and changes

• Added parsing of VHTCapabilities
• Handles VHT MCS and HT MCS.
• Uses "golang.org/x/sys/unix" instead of "github.com/mdlayher/wifi/internal/nl80211"
• Uses c.get instead of c.execute wherever appropriate in getPHYs()

As this PR includes the first lines of Go code I've written (and copied thanks to dhduvall). This will probably need some review :) Suggestions for improvements are welcome!

[SuperQ]

Looks like there are some errors.

[SuperQ]

Any interest in finishing this?