Added missing headers in Interdomain and Slice component files

src/interdomain/__init__.py

src/interdomain/client/InterdomainClient.py

src/interdomain/service/RemoteDomainClients.py

src/interdomain/service/__init__.py

src/interdomain/tests/test_unitary.py

src/slice/client/SliceClient.py

src/slice/client/__init__.py

src/slice/old_code/ConstraintsChecker.py

src/slice/old_code/SliceCheckers.py

src/slice/old_code/Tools.py

src/slice/old_code/Tools_2.py

src/slice/service/__init__.py

src/slice/tests/__init__.py

src/slice/tests/test_unitary.py