[SPARK-4883][Shuffle] Add a name to the directoryCleaner thread

Author: zsxwing <zsxwing@gmail.com>

Closes #3734 from zsxwing/SPARK-4883 and squashes the following commits:

e6f2b61 [zsxwing] Fix the name
cc74727 [zsxwing] Add a name to the directoryCleaner thread
[Minor] Improve some code in BroadcastTest for short

Using
    val arr1 = (0 until num).toArray
instead of
    val arr1 = new Array[Int](num)
    for (i <- 0 until arr1.length) {
      arr1(i) = i
    }
for short.

Author: carlmartin <carlmartinmax@gmail.com>

Closes #3750 from SaintBacchus/BroadcastTest and squashes the following commits:

43adb70 [carlmartin] Improve some code in BroadcastTest for short
[SPARK-4733] Add missing prameter comments in ShuffleDependency

Add missing Javadoc comments in ShuffleDependency.

Author: Takeshi Yamamuro <linguin.m.s@gmail.com>

Closes #3594 from maropu/DependencyJavadocFix and squashes the following commits:

32129b4 [Takeshi Yamamuro] Fix comments in @aggregator and @mapSideCombine
303c75d [Takeshi Yamamuro] [SPARK-4733] Add missing prameter comments in ShuffleDependency
SPARK-4447. Remove layers of abstraction in YARN code no longer needed after dropping yarn-alpha

Author: Sandy Ryza <sandy@cloudera.com>

Closes #3652 from sryza/sandy-spark-4447 and squashes the following commits:

2791158 [Sandy Ryza] Review feedback
c23507b [Sandy Ryza] Strip margin from client arguments help string
18be7ba [Sandy Ryza] SPARK-4447
[SPARK-4079] [CORE] Consolidates Errors if a CompressionCodec is not available

This commit consolidates some of the exceptions thrown if compression codecs are not available. If a bad configuration string was passed in, a ClassNotFoundException was through. Also, if Snappy was not available, it would throw an InvocationTargetException when the codec was being used (not when it was being initialized). Now, an IllegalArgumentException is thrown when a codec is not available at creation time - either because the class does not exist or the codec itself is not available in the system. This will allow us to have a better message and fail faster.

Author: Kostas Sakellis <kostas@cloudera.com>

Closes #3119 from ksakellis/kostas-spark-4079 and squashes the following commits:

9709c7c [Kostas Sakellis] Removed unnecessary Logging class
63bfdd0 [Kostas Sakellis] Removed isAvailable to preserve binary compatibility
1d0ef2f [Kostas Sakellis] [SPARK-4079] [CORE] Added more information to exception
64f3d27 [Kostas Sakellis] [SPARK-4079] [CORE] Code review feedback
52dfa8f [Kostas Sakellis] [SPARK-4079] [CORE] Default to LZF if Snappy not available
[SPARK-4864] Add documentation to Netty-based configs

Author: Aaron Davidson <aaron@databricks.com>

Closes #3713 from aarondav/netty-configs and squashes the following commits:

8a8b373 [Aaron Davidson] Address Patrick's comments
3b1f84e [Aaron Davidson] [SPARK-4864] Add documentation to Netty-based configs