[Docs] Replace references to SchemaRDD with DataFrame

Author: Reynold Xin <rxin@databricks.com>

Closes #4952 from rxin/schemardd-df-reference and squashes the following commits:

b2b1dbe [Reynold Xin] [Docs] Replace references to SchemaRDD with DataFrame

python/pyspark/ml/pipeline.py

@@ -39,7 +39,7 @@ class Estimator(Params):
         Fits a model to the input dataset with optional parameters.
 
         :param dataset: input dataset, which is an instance of
-                        :py:class:`pyspark.sql.SchemaRDD`
+                        :py:class:`pyspark.sql.DataFrame`
         :param params: an optional param map that overwrites embedded
                        params
         :returns: fitted model
@@ -62,7 +62,7 @@ class Transformer(Params):
         Transforms the input dataset with optional parameters.
 
         :param dataset: input dataset, which is an instance of
-                        :py:class:`pyspark.sql.SchemaRDD`
+                        :py:class:`pyspark.sql.DataFrame`
         :param params: an optional param map that overwrites embedded
                        params
         :returns: transformed dataset

python/pyspark/ml/wrapper.py

@@ -102,7 +102,7 @@ class JavaEstimator(Estimator, JavaWrapper):
         """
         Fits a Java model to the input dataset.
         :param dataset: input dataset, which is an instance of
-                        :py:class:`pyspark.sql.SchemaRDD`
+                        :py:class:`pyspark.sql.DataFrame`
         :param params: additional params (overwriting embedded values)
         :return: fitted Java model
         """

repl/scala-2.11/src/test/scala/org/apache/spark/repl/ReplSuite.scala

@@ -263,14 +263,14 @@ class ReplSuite extends FunSuite {
     assertDoesNotContain("Exception", output)
   }
 
-  test("SPARK-2576 importing SQLContext.createSchemaRDD.") {
+  test("SPARK-2576 importing SQLContext.createDataFrame.") {
     // We need to use local-cluster to test this case.
     val output = runInterpreter("local-cluster[1,1,512]",
       """
         |val sqlContext = new org.apache.spark.sql.SQLContext(sc)
-        |import sqlContext.createSchemaRDD
+        |import sqlContext.implicits._
         |case class TestCaseClass(value: Int)
-        |sc.parallelize(1 to 10).map(x => TestCaseClass(x)).toSchemaRDD.collect
+        |sc.parallelize(1 to 10).map(x => TestCaseClass(x)).toDF.collect
       """.stripMargin)
     assertDoesNotContain("error:", output)
     assertDoesNotContain("Exception", output)