Switch to OWM location id instead of city,country query

[marcelstoer]

Prerequisite for fixing ThingPulse/esp8266-weather-station-color#81

[squix78]

Thanks for the PR. I would have suggested to add a a second update method and leave it to the users which one to call. The City,Country method is very easy if not perfect for beginners, while the one by ID is perfect but potentially intimidating for beginners. Since this is for educational purposes we should offer both. What do you think?

[marcelstoer]

Alright, will do as follows:

• new functions updateCurrentById, updateForecastsById to avoid introducing breaking changes
• extract the URL-building part into function to be reused by both before calling doUpdate
• demos will use the new functions
• add comment in settings.h as for how to obtain the right location id
• once released I'll update the other clients accordingly