remove two blank images (useless and slower than Null())
clarify in weather.rpy which are images directly shown on the screen and not just ingredients for the others
simplify the screen code
* Replaced one-off screen effects with images
* Restructured objects and decorations image files and placed them in the relevant room directories
* Moved some image definitions into relevant mirror story scripts
* Removed old interface assets
* Reimplemented weather using renpy image methods
* Fixed weather causing fps drop
* Added cached weather results to the main room
* Reduced animation overhead
* Removed weather screen
* Unified day and night cloud images
