Provide TNO fork of JFreeChart as third party library

While awaiting the official release of JFreeChart 1.6.0 (see #4), provide the binaries of its TNO fork at https://github.com/Yuri-Blankenstein-TNO/jfreechart/tree/v1.6.0_RC1 as third party library in the git repository. The usage of JFreeChart has been approved, see CQ 23674