Add online query editor and visualizer

[keski]

We should consider adding a query editor and result visualizer to the web service in the style of Fuseki. I'd suggest basing this on YASGUI since it provides it all in a nice package.

[keski]

We could also consider whether its possible to load the service URLs from the config files and use these for auto-completion.

[hartig]

I totally agree that this would be something very nice to have!!

(But please don't start working on it right away. We have several other things that need to be done and we may have to prioritize.)