Add IPMI pollster

New pollster to get IPMI sensor data and Intel Node Manager data. IPMI sensor
data includes main types, like Current, Temperature, Voltage and Fan. Node
manager data includes system power and thermal information.

Implements bp ipmi-support
DocImpact: Add new ipmi agent and pollsters

Change-Id: I4e21711cfdb050488dd2ddda1ca80504e63eafaa
Signed-off-by: Zhai Edwin <edwin.zhai@intel.com>