Extend tests coverage (#1476)

Now there is at least one flow under `tests/pcap` for 249 protocols out
of the 284 ones supported by nDPI.

The 35 protocols without any tests are:

* P2P/sharing protocols: DIRECT_DOWNLOAD_LINK, OPENFT, FASTTRACK,
EDONKEY, SOPCAST, THUNDER, APPLEJUICE, DIRECTCONNECT, STEALTHNET

* games: CSGO, HALFLIFE2, ARMAGETRON, CROSSFIRE, DOFUS, FIESTA,
FLORENSIA, GUILDWARS, MAPLESTORY, WORLD_OF_KUNG_FU

* voip/streaming: VHUA, ICECAST, SHOUTCAST, TVUPLAYER, TRUPHONE

* other: AYIYA, SOAP, TARGUS_GETDATA, RPC, ZMQ, REDIS, VMWARE, NOE,
LOTUS_NOTES, EGP, SAP

Most of these protocols (expecially the P2P and games ones) have been
inherited by OpenDPI and have not been updated since then: even if they
are still used, the detection rules might be outdated.

However code coverage (of `lib/protocols`) only increases from 65.6% to
68.9%.

Improve Citrix, Corba, Fix, Aimini, Megaco, PPStream, SNMP and Some/IP
dissection.
Treat IPP as a HTTP sub protocol.
Fix Cassandra false positives.

Remove `NDPI_PROTOCOL_QQLIVE` and `NDPI_PROTOCOL_REMOTE_SCAN`:
these protocol ids are defined but they are never used.

Remove Collectd support: its code has never been called. If someone is
really interested in this protocol, we can re-add it later, updating the
dissector.

Add decoding of PPI (Per-Packet Information) data link type.

python/ndpi.py

@@ -577,9 +577,6 @@ struct ndpi_flow_tcp_struct {
   /* NDPI_PROTOCOL_SKYPE */
   uint8_t skype_packet_id;
 
-  /* NDPI_PROTOCOL_CITRIX */
-  uint8_t citrix_packet_id;
-
   /* NDPI_PROTOCOL_LOTUS_NOTES */
   uint8_t lotus_notes_packet_id;
 

python/ndpi_typestruct.py

@@ -352,7 +352,6 @@ class NDPIFlowTcpStruct(Structure):
         ('mail_imap_stage', c_uint32, 3),
         ('mail_imap_starttls', c_uint32, 2),
         ('skype_packet_id', c_uint8),
-        ('citrix_packet_id', c_uint8),
         ('lotus_notes_packet_id', c_uint8),
         ('teamviewer_stage', c_uint8),
         ('prev_zmq_pkt_len', c_uint8),