temperature default sensor

Default sensor is first input of first device. Sometimes this does not match the CPU temperature sensor.

sudo sensors
acpitz-virtual-0
Adapter: Virtual device
temp1:        +25.0°C  (crit = +107.0°C)

coretemp-isa-0000
Adapter: ISA adapter
Physical id 0:  +71.0°C  (high = +100.0°C, crit = +100.0°C)
Core 0:         +69.0°C  (high = +100.0°C, crit = +100.0°C)
Core 1:         +71.0°C  (high = +100.0°C, crit = +100.0°C)

dell_smm-virtual-0
Adapter: Virtual device
Processor Fan: 5633 RPM
CPU:            +71.0°C  
Ambient:        +49.0°C  
SODIMM:         +39.0°C  

cat /sys/class/hwmon/hwmon0/temp1_input 
25000
cat /sys/class/hwmon/hwmon1/temp1_input 
73000

We should scan for sensor during configuration building and give user a choice on which sensor to use for CPU temperature.

This should also be reported in temp_watch LUA function.