This commit brings a few changes that I was too lazy to
split in different commits:
* Remove a few useless arguments in the GcalWeatherService API
* Move the weather management code from GcalWindow to GcalWeatherSettings
* A few style changes
This commit introduces two new classes:
1. GCalWeatherService
2. GCalWeatherInfo
GcalWeatherservice picks-up the current location and periodically
fetches weather reports represented by GcalWeatherInfo.
The weather part is not complete yet.