Added logging to Graph, GraphLab, and Pregel.

graph/src/main/scala/org/apache/spark/graph/Graph.scala

@@ -3,6 +3,7 @@ package org.apache.spark.graph
 
 import org.apache.spark.rdd.RDD
 import org.apache.spark.util.ClosureCleaner
+import org.apache.spark.Logging
 
 
 
@@ -24,7 +25,7 @@ import org.apache.spark.util.ClosureCleaner
  * @tparam VD the vertex attribute type
  * @tparam ED the edge attribute type 
  */
-abstract class Graph[VD: ClassManifest, ED: ClassManifest] {
+abstract class Graph[VD: ClassManifest, ED: ClassManifest] extends Logging {
 
   /**
    * Get the vertices and their data.

graph/src/main/scala/org/apache/spark/graph/GraphLab.scala

@@ -2,11 +2,12 @@ package org.apache.spark.graph
 
 import scala.collection.JavaConversions._
 import org.apache.spark.rdd.RDD
+import org.apache.spark.Logging
 
 /**
  * This object implements the GraphLab gather-apply-scatter api.
  */
-object GraphLab {
+object GraphLab extends Logging {
 
   /**
    * Execute the GraphLab Gather-Apply-Scatter API

graph/src/main/scala/org/apache/spark/graph/Pregel.scala

 package org.apache.spark.graph
 
 import org.apache.spark.rdd.RDD
+import org.apache.spark.Logging
 
 
 /**
@@ -41,7 +42,7 @@ import org.apache.spark.rdd.RDD
  * }}}
  *
  */
-object Pregel {
+object Pregel extends Logging {
 
 
   /**