[PROJ] proj4.org -> proj.org migration

[Even Rouault]

> I have now changed the repo name to PROJ (previously proj.4). New GitHub
> URL
 is https://github.com/OSGeo/PROJ. I have done a few tests on my local
> git clone without updating the URL and URL-redirecting seems to be working
> fine. Please let me know if you encounter any problems.

There was an issue with coveralls that was no longer updated, which prevented 
the following step in Travis-CI, website building, to be run. So I've created
https://coveralls.io/github/OSGeo/PROJ and things are now back to work.
I guess we should now delete the old https://coveralls.io/github/OSGeo/proj.4 
to avoid confusion ?
Similarly I've created https://ci.appveyor.com/project/OSGeo/PROJ, and
https://ci.appveyor.com/project/OSGeo/proj-4 should be deleted ?

Even

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