Integration of Daniel's BLOB manager

I rebased the pull request #107 of @warneke. Thanks for your work Daniel, the code looks really good. Since the master evolved a little bit from the version of the pull request, I'd like to have another pair of eyes looking over it. I tried to address the problem of old jar files which are no longer used by introducing a clean up task which regularly looks for those files. Due to this I had to extend the book keeping of the LibraryCacheManager a little bit.

I tested WordCount and Kmeans on the cluster with this version.
Is that really in the sense of what the streaming folks had in mind? Probably makes little difference when everything is in the same JVM, but in general, I think such edits should not be mixed into other pull requests.