Improve confusing / inaccurate exceptions

[Aklakan]

I started a wiki page for queries with errors. LSQ2 should catch most exceptions and continue anyway, however, in some cases this results in a generic ''internal error" message' when in fact LSQ2 is functioning fine, however an incorrect query made it into the benchmarking pipeline. There are many reasons how this can happen; an odd one was a due to a bug in jena's shallowClone (fixed by now) which raised an exception for perfectly fine queries.

In any case, exception handling should be improved such that no more generic "internal error" message is needed.

https://github.com/AKSW/LSQ/wiki/Erroneous-Queries