Updates of comments and correcting bugs in hull update procedure (INCREMENTAL one, which simply added a new non-cover object as an additional hull object). Now it does the optimization, i.e., replacing a existing hull object before adding the new object as a new hull object.

* ApproxKnn oper changed to its predecessor Knn oper

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

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