[SPARK-12665][CORE][GRAPHX] Remove Vector, VectorSuite and GraphKryoRegistrator which are deprecated and no longer used

Whole code of Vector.scala, VectorSuite.scala and GraphKryoRegistrator.scala  are no longer used so it's time to remove them in Spark 2.0.

Author: Kousuke Saruta <sarutak@oss.nttdata.co.jp>

Closes #10613 from sarutak/SPARK-12665.