Remove files no longer used in the 3.0 RC2 version of the spec

[goneall]

Fixes #881

[goneall]

@licquia @zvr - Please review - I tried to clean this up based on the information I have, but it looks like there is a lot of additional changes that need to be made to mkdocs configs etc.

[goneall]

@licquia If this doesn't make the mkdocs work any worse, I'd like to merge this in - let me know.

[kestewart]

Thanks Gary, lots of changes here, but from a review, I think you've caught most of what's been discussed. @licquia - can you take a look this doesn't cause problems for the work you've been doing, and then we can merge.

[zvr]

I'd also delete the examples subdirectory (and its README), since they are not part of the docs.
And rename the RDF... annex to be about "graphical representations" or something.

But we can do all this via another PR, after also updating mkdocs configuration.

So, let's go ahead and merge this.

[goneall]

I'm going to go ahead and merge this and see if I can help @licquia with the PDF / HTML generation.