ActionInterface: move API documentation to the header
ActionInterface: add method SendUIState()
UIState: add struct WeatherUIState

Use UIState to communicate the RASP map selection to the MapWindow.
Terrain/RasterWeather: split class

RasterWeatherStore manages the list of map items in the ZIP file and
loads RasterMap instances, and RasterWeatherCache manages the
item/time selection and manages the RasterMap instance.