[Python 2 to 3] Exceptions, loops, isinstance and haskey

[General] Update licenses & Contrib flags

Better winpcap/npcap control: scapy is now able to detect the offline
service and start it manually

[convergence] map() calls rewritten as list comprehensions

Fix typo in troubleshooting.rst

(or its equivalent on other systems that Linux) => (or its equivalent on other systems than Linux)

fix nsh len field init

Since MDType default value is 1, set Len defautl value to 6

Also add a post_build function which sets the len value to len(pkt)/4

fix scapy tests accordingly

Support (in contrib) for MQTT (Message Queue Telemetry Transport) protocol, with tests.

[coverage] More tests for inet.py

Modify information about sr() and fuzz()

Cleanup Nmap module, add tests

Added information about sr() and fuzz() functions, nothing important but useful as well.

Signed-off-by: Fernando Fernández <ffernandezmancera@gmail.com>

[TLS] Unify UTCTimeField (small)

Replace the UTCTimeField occurences (one in ppi_geotag.py, one in dhcp6
and one in tls/handshake) by a single one

[Python 2 to 3] Remove longs and fix octals