bug fixed: giving the order to train an archer without having a lumber mill was silently ignored by the game (no negative sound)
refactoring: cleaning more imports
bug fixed: now the shortcut for town hall is "h" instead of "t" ("t" is for towers)
turned all the secondary threads into daemon threads

This way the game will instantly stop when the main thread ends, for example when closing the game window.
refactoring: added close_media(); call pygame.quit() so the game can quit even from Idle