[SPARK-9100] [SQL] Adds DataFrame reader/writer shortcut methods for ORC

[liancheng]

This PR adds DataFrame reader/writer shortcut methods for ORC in both Scala and Python.

[chenghao-intel]

Nit: Also add examples like you did at DataFrameWriter?

• This is equivalent to:
• {{{
• format("orc").load(path)
• }}}

[liancheng]

The one in DataFrameWriter isn't an example, it says that method is equivalent to format("orc").load(path).

[SparkQA]

Test build #37497 has finished for PR 7444 at commit e0b09fb.

• This patch fails PySpark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[rxin]

you should document this is only available if hive is ...

[liancheng]

Yeah, right. Thanks for reminding!

[liancheng]

@rxin @davies A little off topic, but python/pyspark/sql/readwriter.py should probably be renamed to readerwriter.py or readwrite.py. Which do you prefer?

[SparkQA]

Test build #37616 has finished for PR 7444 at commit 284d043.

• This patch fails PySpark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[liancheng]

retest this please

[SparkQA]

Test build #37640 has finished for PR 7444 at commit 284d043.

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

[rxin]

lgtm

[liancheng]

Thanks for the review, merging to master.