Need to fix up copyrights for openjfx docs to use GPLv2 or BSD licenses

Several of the docs in the openjfx repo have Oracle proprietary copyright headers or links to Oracle proprietary licenses. These should be fixed so that the sources for these docs in the repo have open-source licenses (either GPLv2 or BSD) and have the build for Oracle FX take care of substituting the Oracle proprietary copyright at build time.

This affects at least the following: the javadoc footer, the cssref.html doc (which we handled tactically for FX 8 in RT-34389 by making a build time copy with a BSD license to accompany the samples), introduction_to_fxml.html, and the javafapackager.1 man page.