~ Core: Source added to the WeatherData
~ Core: weather api clients visibility
+ Core: IWeatherDataAggregator
+ Core: AvgWeatherDataAggregator
~ Core: csproj fix
+ Core: Weather data aggregator factory
+ Core: weather data cache factory
~ Core: constant city info provider visibility
~ Web: use IWeatherDataAggregator for aggregation
~ Web: use WeatherDataCacheFactory instead of concrete implementation