Visualcrossing

[drechc]

• 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.

This adds a few enhancements to the WeatherStationDemo:

• Switches to a more robust version of the configTime function. The current version doesn't support variations of daylight saving time used in some countries.
• Removes the decimal for Fahrenheit temperatures, as they aren't typically reported with one. Also, it can make the value too long to fit for temps >=100F.
• Adds option for 12-hour time display for users that prefer it.
• Add options for various date orders to support countries that don't use D/M/Y order.
• Adds VisualCrossing as a new source option for free weather data and adds a new demo implementing this source. Both are based on the OpenWeatherMap code. The data from OpenWeatherMap didn't seem very accurate in my area, and VisualCrossing worked better for me.