Compare RDF parser for best error output

[np00]

Study at least the following ones:

• rapper (BTW in order to run make in https://github.com/mobivoc/mobivoc you will need rapper anyway)
• rdfcat

[clange]

BTW, with vocol/mobivoc@d3d43c9 I fixed some syntax errors. At the moment, no *.ttl file has any remaining syntax errors, so you need to introduce some on your own, or, what's better (with a more comprehensive evaluation in mind), use old versions of the files, which contain real errors.

[clange]

BTW I'd try to see how far we get with processing the console error output of these tools. Instead of rdfcat we could also write our own Java program that uses Jena, or some C program instead of rapper. It will be more work to write such programs, but, as @lavdim pointed out, we may get more precise information about syntax errors.

Note, however, the the more important point is what tool reports most errors when there are multiple errors in a file.

[np00]

The script https://github.com/mobivoc/vocol/blob/master/validator/run_statistics.py
can be used to compare validators.