Add support for OWM One Call API

[c-klinger]

https://openweather.co.uk/blog/post/new-one-call-api-essential-weather-data

Fixes #182

• This PR is compliant with the other contributing guidelines as well (if not, please describe why).
• I have thoroughly tested my contribution.
• Should this code require changes to documentation I will contribute those to https://github.com/ThingPulse/docs.

[marcelstoer]

Looks fine, thanks for your contribution:

• Can you please add an example along the lines of the existing OpenWeatherMapForecastDemo or OpenWeatherMapCurrentDemo
• There is undoubtedly value in self-contained OpenWeatherMapXYZ .h and .cpp files. However, it also adds maintenance overhead as large chunks of code are inevitably identical. Reuse by copy-pasting code is never ideal. How do you feel about refactoring the (now three) integrated APIs under a common umbrella? Any thoughts on this?