[TOREE-536] AddJar command to support Google cloud storage (#200)

Author: ywskycn

kernel/src/main/scala/org/apache/toree/magic/builtin/AddJar.scala

@@ -30,7 +30,7 @@ import org.apache.hadoop.fs.Path
 import org.apache.toree.plugins.annotations.Event
 
 object AddJar {
-  val HADOOP_FS_SCHEMES = Set("hdfs", "s3", "s3n", "file")
+  val HADOOP_FS_SCHEMES = Set("hdfs", "s3", "s3n", "file", "gs")
 
   private var jarDir:Option[String] = None