Move OGCAPISimple to its own Repository

[hylkevds]

I think it would be good to move the OGCAPISimple to its own repository, with a more standard layout. That way users don't have to download the irrelevant other parts of this repository, and search for where the source code is, when they want to get OGCAPISimple.

[hylkevds]

I've set up a (sort of) mirror on https://github.com/hylkevds/OGCApiSimple, with only the OGCApiSimple code.
I also removed the war file from there, since that should not be in the source-code repo.
Lastly, I set it up to auto-build on travis, and push to docker:
https://hub.docker.com/repository/docker/fraunhoferiosb/ogcapisimple