* KMeans pivots chooser and hierarchical chooser

* New dump structure operation
* KNN operation fixes the number of objects added (upon refining its answer)
* KMeans pivots chooser and hierarchical chooser

* Updated java compiler parameters in POM
* Added support for shutdown hook registration

Master

Approved-by: David Novak <novak.david@gmail.com>

minor convenience updates; float vector's method toString now prints the raw data (needed for GetObjectOperation#answer called by CoreApplication)

Batch ranking query

major update that adds an UpdateLog that is automatically replayed in case of a hard system fall

Alow construction of BatchKNNQueryOperation using any Iterator,
not only StreamGenericAbstractObjectIterator

Master

 * removing one constructor from JoinQO that had the same number of arguments as other constructor that was used more often

 * randompivotchooser marked as deprecated, because it does not select the pivots uniformly; it took me about 8 hours of my time

 * LocatorQueryOperation now allows more than one query locator
 * RefineCandidate operation generalized to be applicable also to multi-query operations
 * KNN RankByLocator allows more than one query locator
 * added new multi-query average distances (geometric mean and harmonic mean)

 * adding new options in aggregation function

* Added a few tests for the sorting iterator