This fixes the redistribution of candidate
hull objects during node splitting.

* Fixed bug causing SUM_DIST to always return -0.5.
* Extended the ObjectToNodeDistance class to accept
  also a list of objects instead of node.

Same ranking function is used for inserting
objects and searching in the MH-Tree.

MH-Tree:
* format statistics better
* fix swapped fields in statistics
* make balancing and ancestor recomputation configurable

benchmarks:
* shuffle datasets before benchmarking
* enhance names of command-line options
* iterate over split types only when they are provided

* benchmark output directory is configurable,
  benchmark output is unified
* picocli used for CLI management

* New methods in MH-Tree -- exact-match search & fat factor