taxonomy: implement v3 signature format.

The TX Power levels from the Association Request
appear to be very useful for disambiguating
devices which are otherwise very similar, for example:
+ Apple iPhone 5 from iPad 4th gen from iPad Mini 2nd gen
+ Samsung Galaxy Note 4 from Galaxy S5

Also include the capabilities field from the Association
Request, as that is more distinctive than we believed
at first.

Extended Capabilities can be longer than 4 bytes.
Include whatever is there.

Change-Id: Ife1fa3f69c1c93be5745edd0347707171faedad9
3 files changed