Definitions for PBI coder

Added support for PBI coder (only PBI DCH-4000P, may work for DCH-5000P).

MIBs:
https://data.nag.ru/PBI/SNMP%20MIBs/4000P-MIB-v1.69-b.rar

In this patch:

• mibs/pbi/PBI-4000P-5000P-MIB
• mibs/pbi/PBI-MAIN-MIB
• mibs/pbi/PBI-MGSIGNALCHARACTERISTICS-MIB
• mibs/pbi/PBI-MGSYSTEM-MIB
• includes/definitions/vendors.inc.php
  • new vendor http://www.pbi-china.com/
• includes/definitions/os.inc.php
  • new OS "pbi-coder"
• includes/definitions/mibs/pbi.inc.php
  • PBI-MGSYSTEM-MIB
    • serial
  • PBI-4000P-5000P-MIB
    • discover ipv4 addresses from MGMT interface and from TS/IP Input/Output interface
    • no interface discovery - only mac addresses is "easy" to get, but not used
    • status linkStatus (Off, 10MB, 100MB)
    • many statuses
    • sensor tunerTotalBitrate – added as gauge (don't find a way to add it as graph in definition)
    • sensor tunerValidBitrate – added as gauge (don't find a way to add it as graph in definition)
    • sensor asiTotalBitrate – added as gauge (don't find a way to add it as graph in definition)
    • sensor asiValidBitrate – added as gauge (don't find a way to add it as graph in definition)
    • sensor tunerStrength – dbm
    • sensor tunerBER – snr
    • sensor tunerCN (Tuner Carrier/Noise) – snr
    • sensor tunerEbNo – snr
    • sensors for tuner-sInput (Satellite input / DVB-S)
    • sensors for s2Input (second Satellite input / DVB-S)
    • sensors for tuner-cInput (Cable input / DVB-C)
    • sensors for tuner-tInput (terrestrial input / DVC-T)
    • satuses for output source