Added channel width detection to the BssNetworkInfo class.

[hagenson]

I have a need to know the bandwidth width of detected wireless networks, so I've added that functionality. I was unable to add a unit test because the test project does not build because of a missing class. I didn't want to mess with that without knowing why.

[emoacht]

Thank you for the PR.
First of all, could you direct me to the information source for how to parse the information element?
The documentation says that "Each information element is assigned a unique Element ID value as defined in this IEEE 802.11 standards" and so there should be such standards that the original author used as reference.