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

* RunBenchmark improved by calling Fat Factor and making M-tree code parallel.