Ensure all source files have Apache Headers

[JohnMcW]

The following files have been reported as not having the Apache licence header:

./.travis.yml
./.gitignore ./Dockerfile ./Dockerfile-alpine ./build-static.sh ./build.sh ./go.mod ./go.sum ./lint.sh ./report ./test.sh ./cmd/servicetester/e2e_test.sh ./cmd/servicetester/fulltest.sh ./cmd/servicetester/id_test.sh ./libs/crypto/libpqnist/CMakeLists.txt ./libs/crypto/libpqnist/CPackConfig.cmake ./libs/crypto/libpqnist/VERSION ./libs/crypto/libpqnist/cmake_uninstall.cmake.in ./libs/crypto/libpqnist/examples/CMakeLists.txt ./libs/crypto/libpqnist/include/CMakeLists.txt ./libs/crypto/libpqnist/src/CMakeLists.txt ./libs/crypto/libpqnist/test/smoke/CMakeLists.txt ./libs/crypto/libpqnist/testVectors/aes/CBCMMT256.rsp ./libs/documents/docs.pb.go ./libs/documents/docs.proto ./libs/documents/docs.validator.pb.go ./pkg/safeguardsecret/README.md ./pkg/safeguardsecret/open-api.yaml

Please add the header where possible/appropriate. Any files that can't or should not have header files should be listed here so we can document why.