Also fix a few bugs and other weirdness in Platform::DirectorySearch. Empty string paths would crash and filenames with 4 or fewer characters wouldn't register.
Also fix the first mouse click not being detected on windows with sdl 2.0.20. Apparenlty, we need SDL_HINT_MOUSE_FOCUS_CLICKTHROUGH set to 1 for it to be detected.
Summary of migrated files will be shown to user in a popup, and a log file with every moved file will be left in the original directory
stamps, saves, scripts, screenshots, and powder.pref will be migrated. Recordings are not.