Checkstyle requires LF line endings: add .gitattributes hint

Running the Java unit tests on a Windows machine with the commonly configured git line ending configuration:

git config --global core.autocrlf true

Results in test failure of:

NewlineAtEndOfFile: Expected line ending for file is LF(\n), but CRLF(\r\n) is detected.

This is due to a checkstyle rule.   If the unit tests require LF line endings then it would be helpful to add a .gitattributes file to automatically ensure the correct line endings are used on git clone.