Client-side only, texture color cache

Remove every trace of server-sideness, fixes https://github.com/RandomMcSomethin/fallingleaves/issues/2, details in https://github.com/RandomMcSomethin/fallingleaves/issues/2#issuecomment-724208550.
adds a cache for texture colors Warning: untested, I'm not sure where this actually happens, I never found an instance where j was -1
~~hack for compatibility with BetterEnd; forces creation of particles even if their type is not in the registry This should be removed once a proper fix comes around~~

RandomMcSomethin / fallingleaves