Complete deviceinterface information

[Wojtek242]

Closes #13

It turns out that since the original issue was create 7 years ago almost everything has been added to the Device struct. The only thing remaining were the flags documented at: https://www.tcpdump.org/manpages/pcap_findalldevs.3pcap.html.

This field was slightly problematic as it consisted of two separate items really:

• interface flags, which were actual single-bit flags
• connection status, which was a 2-bit bitmask behind which were 4 enum-like values identifying the connection status

In the end I opted to create a wrapper struct that separates these two. My previous iteration without this wrapper is in commit 606bdc3.

[Wojtek242]

@Stargateur, would you mind doing a review?