Migrate content from December's EA release notes

https://jdk8.java.net/fxarmpreview/javafx-arm-developer-preview.html

to https://wiki.openjdk.java.net/display/OpenJFX

We don't need to get into detail about how to configure the device, but some things need to be explained - like that it runs on the framebuffer without X11 and that media and web are not available.