Add ConcurrencyBalancer to handle redis semaphores
Add ConcurrencyBalancer to handle redis semaphores

This is needed for OntologyParsing where multiple
ontologies import another one. This should
help to avoid race conditions.

ontohub/ontohub,ontohub/ontohub,ontohub/ontohub,ontohub/ontohub,ontohub/ontohub,ontohub/ontohub