Adding flexible_weather

I set out to play around with my CAD in preparation for a project I wanted to use it for, and ended up building a complete app around weather.py. You can define any number of custom display formats and cycle through them with button 4. The data is never older than the refresh interval, so you can glance at the display and be assured that it's current.

When I was finished and trying to figure out how to submit an updated version, I realized that my version was probably way too complex for a newbie to understand. For that reason I submitted this as a new script.