Extending license to 2021: changed missing files

LICENSE.md

-Copyright 2015-2020 Institute of Technical Acoustics, RWTH Aachen University. Any usage and distribution is prohibited, unless explicitly granted by the authors.
\ No newline at end of file
+Copyright 2015-2021 Institute of Technical Acoustics, RWTH Aachen University. Any usage and distribution is prohibited, unless explicitly granted by the authors.
\ No newline at end of file

README.md

@@ -6,7 +6,7 @@ ITAFFT is a component of [ITACoreLibs](https://git.rwth-aachen.de/ita/ITACoreLib
 
 ### License
 
-Copyright 2015-2020 Institute of Technical Acoustics, RWTH Aachen University
+Copyright 2015-2021 Institute of Technical Acoustics, RWTH Aachen University
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use files of this project except in compliance with the License.