Add support to monitor CPU temperature

[ffeldbauer]

Added support to monitor the CPU temperature on Linux. New function uses the LOAD_TYPE scan rate like all the other CPU related informations.

[ffeldbauer]

Sorry for not responding so long regarding my merge request #45
I was busy preparing our Detector setup for a beamtime and was not able to look into the issue regarding the broken CI.

When I tried to merge the latest master into my fork, I ran into a few new issues, which is why I started from a fresh clone of the current master and added my changes to it

[JJL772]

/sys/class/thermal/thermal_zone0 on my system corresponds to ACPI interface temperature. you might need to iterate each thermal_zone and check the type file in each of them.
for me, thermal_zone4 had type x86_pkg_temp, which seems to match up with the CPU package temperature displayed by lm-sensors.

[jeonghanlee]

@ffeldbauer Thank you for bring this subject again. And please check the previous discussion at #7 with @ralphlange

You may find his insights on this pull request.