Bugfix for non-closed result requestor (task didn't stop). Refactoring.
* Result requestor now closes correctly in JSONResultFacade#retrieveResults()
* Cluster-scope querying mechanics moved to Persistence, which is available from ClusterContext
* BeenAPI supports rudimentary querying

relates to #116
Merge branch 'master' of github.com:radek-macha/everBeen