merge package org.apache.spark.streamdm.util with org.apache.spark.streamdm.utils.
move Statistics from package org.apache.spark.streamdm.util to org.apache.spark.streamdm.utils.
move part functions from org.apache.spark.streamdm.util.Util.scala to org.apache.spark.streamdm.utils.Utils.scala and org.apache.spark.streamdm.classifiers.trees.Utils.scala
3 modify related references.
merge package org.apache.spark.streamdm.util with org.apache.spark.streamdm.utils.