Push UAV forecast to farmcalendar

[fedjo]

Change

• Fetch and cache uav models from FC
• Create activity type to post flight forecast to FC
• Add job to get UAV flight forecast for the next 5 days and post it to FC as Observations

Small changes

• Rename dao function create_point -> find_or_create_point
• Extract correct precipitation value by dividing precipitation/3h (taken from OpenWeatherMap) by 3
• Change numericValue to hasValue in THI Observation see Bug: THI Observation uses numericValue instead of hasValue #37

Relates #29

Adresses #37 #34

[arruda]

Only two small comments, but neither are a major thing, more like a footnote on the mind for future improvements.
One is the numericValue that is not longer in the observation.
The other comment is that it might be helpful to have the endpoints for FC as config env vars (with a default value set). This probably will make the transition to using the gatekeeper easier in the future.