[SPARK-2889] Create Hadoop config objects consistently.

Different places in the code were instantiating Configuration / YarnConfiguration objects in different ways. This could lead to confusion for people who actually expected "spark.hadoop.*" options to end up in the configs used by Spark code, since that would only happen for the SparkContext's config.

This change modifies most places to use SparkHadoopUtil to initialize configs, and make that method do the translation that previously was only done inside SparkContext.

The places that were not changed fall in one of the following categories:
- Test code where this doesn't really matter
- Places deep in the code where plumbing SparkConf would be too difficult for very little gain
- Default values for arguments - since the caller can provide their own config in that case

Author: Marcelo Vanzin <vanzin@cloudera.com>

Closes #1843 from vanzin/SPARK-2889 and squashes the following commits:

52daf35 [Marcelo Vanzin] Merge branch 'master' into SPARK-2889
f179013 [Marcelo Vanzin] Merge branch 'master' into SPARK-2889
51e71cf [Marcelo Vanzin] Add test to ensure that overriding Yarn configs works.
53f9506 [Marcelo Vanzin] Add DeveloperApi annotation.
3d345cb [Marcelo Vanzin] Restore old method for backwards compat.
fc45067 [Marcelo Vanzin] Merge branch 'master' into SPARK-2889
0ac3fdf [Marcelo Vanzin] Merge branch 'master' into SPARK-2889
3f26760 [Marcelo Vanzin] Compilation fix.
f16cadd [Marcelo Vanzin] Initialize config in SparkHadoopUtil.
b8ab173 [Marcelo Vanzin] Update Utils API to take a Configuration argument.
1e7003f [Marcelo Vanzin] Replace explicit Configuration instantiation with SparkHadoopUtil.
SPARK-3318: Documentation update in addFile on how to use SparkFiles.get

Rather than specifying the path to SparkFiles we need to use the filename.

Author: Holden Karau <holden@pigscanfly.ca>

Closes #2210 from holdenk/SPARK-3318-documentation-for-addfiles-should-say-to-use-file-not-path and squashes the following commits:

a25d27a [Holden Karau] Update the JavaSparkContext addFile method to be clear about using fileName with SparkFiles as well
0ebcb05 [Holden Karau] Documentation update in addFile on how to use SparkFiles.get to specify filename rather than path
MAINTENANCE: Automated closing of pull requests.

This commit exists to close the following pull requests on Github:

Closes #1922 (close requested by 'JoshRosen')
Closes #1356 (close requested by 'pwendell')
Closes #1698 (close requested by 'mengxr')
Closes #254 (close requested by 'mateiz')
Closes #2135 (close requested by 'andrewor14')
[Spark QA] only check code files for new classes

Look only at code files (`.py`, `.java`, and `.scala`) for new classes.

Should get rid of false alarms like [the one reported here](https://github.com/apache/spark/pull/2014#issuecomment-52912040).

Author: Nicholas Chammas <nicholas.chammas@gmail.com>

Closes #2184 from nchammas/jenkins-ignore-noncode and squashes the following commits:

33786ac [Nicholas Chammas] break up long line
3f91a14 [Nicholas Chammas] rename array of source files
8b82a26 [Nicholas Chammas] [Spark QA] only check code files for new classes