[SPARK-5904][SQL] DataFrame Java API test suites.

[rxin]

Added a new test suite to make sure Java DF programs can use varargs properly.
Also moved all suites into test.org.apache.spark package to make sure the suites also test for method visibility.

[SparkQA]

Test build #27920 has started for PR 4751 at commit a6ca53b.

• This patch merges cleanly.

[jkbradley]

organize imports

[jkbradley]

I don't see any other issues

[SparkQA]

Test build #27922 has started for PR 4751 at commit 1e8b8e4.

• This patch merges cleanly.

[SparkQA]

Test build #27920 has finished for PR 4751 at commit a6ca53b.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[AmplabJenkins]

Test PASSed.
Refer to this link for build results (access rights to CI server needed):
https://amplab.cs.berkeley.edu/jenkins//job/SparkPullRequestBuilder/27920/
Test PASSed.

[SparkQA]

Test build #27922 has finished for PR 4751 at commit 1e8b8e4.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):
  • public class JavaApplySchemaSuite implements Serializable
  • public static class Person implements Serializable
  • public class JavaDataFrameSuite
  • public class JavaRowSuite
  • public class JavaUDFSuite implements Serializable
  • public class JavaSaveLoadSuite

[AmplabJenkins]

Test PASSed.
Refer to this link for build results (access rights to CI server needed):
https://amplab.cs.berkeley.edu/jenkins//job/SparkPullRequestBuilder/27922/
Test PASSed.