Turns out, only maybe 1/3 of all available predicates are actually
part of the exported datasets. No surprise my queries are hitting
nothing.

This will be very useful for further integration w/ JVM tech.

I also etst performance and it looks okay on my small laptop.

- This also works just as well as a REST endpoint.

- Most likely this is just a demo. But it works for that.

I'll only need it for a demo, probably. But it's nice to have.

Should be enough to (1) talk to the Java API and (2) provide
a JSON API for the world.

This is really just experimental. MMT should be integrated directly
w/o JSON if possible to avoid nonsensical serialization.

Honestly Play is way too much for what I need. I just need
a simple JSON endpoint.

- I'll need some REST endpoint for the data

- GrahDB uses RDF4J -> JVM language prefered

- Let's try out Play. It works w/ Scala and Java.

- code goes into /src

- prose in /doc

- /experimental is a playground