Peter M. Groen / hueplusplus

…client key with the username

Change reference to value return types.

All resources on the bridge internally use the same json state.
Advantages: Different resources are always consistent.
Disadvantages: Different objects are no longer thread safe, changes are not transparent.

Co-authored-by: Moritz Wirger <lj.moritorii@web.de>

Fix some copy paste errors.

Add definitions for constexpr strings.

Fix some errors in these classes.
Make sensor constructors explicit.

SensorList allows you to directly get the sensor type you want or all sensors of a given type.

- remove redundant Hue prefix
- change Hue class to Bridge class to make usage clearer
- rename APIConfig to LibConfig to clarify that the configuration is for the library, not for the Hue API that is accessed