Improvements to battery monitoring (#1158)

* Check whether battery values are available

* Rename _degradationPercentage to _degradationLevel

* Add support for temperature monitoring

* Include the battery device name and tag in the hardware identifier

* Set sensor index value properly

* Fix temperature conversion

The returned temperature value must be divided, not multiplied.

* Disable sensors that have a "null" value

* Fix random symbols in battery device name and manufacturer