Licenses: Change WTFPL to MIT (part 2)

Add license.txt files.
Update and improve README.txt files.
Corrections to part 1.

mods/flowers/license.txt

@@ -2,8 +2,8 @@ License of source code and media (textures)
 -------------------------------------------
 
 The MIT License (MIT)
-Copyright (C) 2012-2013 Ironzorg, VanessaE (source code)
-Copyright (C) 2015-2016 Gambit (textures)
+Copyright (C) 2012-2013 Ironzorg, VanessaE
+Copyright (C) 2015-2016 Gambit
 
 Permission is hereby granted, free of charge, to any person obtaining a copy of this
 software and associated documentation files (the "Software"), to deal in the Software