TEZ-1614.  Use setFromConfiguration() in SortMergeJoinExample to demonstrate the usage
 (Cherry picked from commit efa6afd0f3e8a5c2cde8f1c415f6b3f87c194c89)
Adding TEZ-1614 to CHANGES.txt
TEZ-1641. Add debug logs in VertexManager to help debugging custom VertexManagerPlugins