There are some compatibility problems with ELK 0.5 that I don't fully understand. What about packaging both ELK 0.4.x and ELK 0.5.x in ROBOT? We would keep ELK 0.4.x as --reasoner elk and add ELK 0.5.x as --reasoner elk5.

The JARs might just conflict too much, but I think we should try.