Move reading of temperature sensors' tresholds from hal to snmp. Thresholds
were and still are read from dot-config.

update:
--hal
--hal_shmem header
--snmpd
--wr_mon
--wrs_dump_shmem
--uplift ppsi (update hal_shmem header)
Signed-off-by: Adam Wujek <adam.wujek@cern.ch>