Merge pull request #5 from Teots/master

Added: Statistics collection | Removed: Resource leaks, EventLoopGroup deadlock
Merge pull request #6 from Teots/master

EventLoopGroup Refactoring
* Implemented a first version of the session concept.
added a session concept in the aura client api, optimized task deployment
removed TopologyRewriter and GenericDirectedGraph
tiny merge corrections
added aura-benchmark module, some reorganizations
close session in all clients, removed TwoTaskTest client
formatted codebase, optimized imports
Merge pull request #7 from TobiasHerb/master

Deployment-Optimizations
Fixed the lost updates problem in our Zookeeper code
Merge branch 'master' of github.com:citlab/AURA