Offer the possibility to monitor t° average or hot spots

[mathoudebine]

Based on https://github.com/mathoudebine/turing-smart-screen-python/pull/140

Is your feature request related to a problem? If so, please describe the problem.
By default, the CPU / GPU temperatures displayed are the cores average

Describe the feature / solution to your problem you'd like
I want to be able to monitor hot spots (max. temperatures) instead of core average, and select it from the Configuration Wizard / config.yaml

Describe alternatives you've considered / and or tested
This PR #140 but it is better to let the user decide