set correct copyright year for all files

This MR sets the correct copyright year (i.e. the year each file was last changed in) for all files.

aas/adapter/json/json_deserialization.py

-# Copyright 2019 PyI40AAS Contributors
+# Copyright 2020 PyI40AAS Contributors
 #
 # Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
 # the License. You may obtain a copy of the License at