Make AbstractNamedBean.getFullyFormattedDisplayName() final

[danielb987]

I also tested to make AbstractNamedBean.toString() final, but that method has a lot of different implementations and I'm afraid to break things if I change that.

The classes with different toString() implementations are:
jmri.jmrit.logix.Portal
jmri.implementation.AbstractAudio
jmri.implementation.AbstractIdTag
jmri.implementation.AbstractStringIO - This is created by me and new so changing it will probably not break anything.
jmri.implementation.DefaultRailCom
jmri.implementation.DefaultSignalSystem
jmri.jmrit.audio.AbstractAudioListener
jmri.jmrit.audio.AbstractAudioSource
jmri.jmrit.audio.JavaSoundAudioBuffer
jmri.jmrit.audio.JoalAudioBuffer
jmri.jmrit.audio.NullAudioBuffer

[danielb987]

Closed and reopened PR due to AppVeyor:

Build started
git clone -q --depth=50 https://github.com/JMRI/JMRI.git C:\projects\jmri
fatal: early EOF
fatal: The remote end hung up unexpectedly
fatal: index-pack failed
error: RPC failed; curl 56 OpenSSL SSL_read: SSL_ERROR_SYSCALL, errno 10054
Command exited with code 128

[danielb987]

This PR is ready to be merged. The discussion of toString() is moved to PR #6463.