core: remove pcap library dependency

Pcap library was slightly used for link layer definitions, to get the
right dpkt decode. We not consider every packet as a ethernet frame.

Signed-off-by: Hagen Paul Pfeifer <hagen@jauu.net>
core: add new decoder functionality

Due to python-pcap removal the packet decoder was enforced to interpret
every packet as Ethernet - which will not be true in every case.

This patch check for some common types (Ethernet, Loopback, Linux) and
if not correct we enforce a Ethernet encoding - which will _probably_
not be correct, but it is better then nothing. A big warning message is
printed.

Signed-off-by: Hagen Paul Pfeifer <hagen@jauu.net>
core: increase version number

Signed-off-by: Hagen Paul Pfeifer <hagen@jauu.net>