SPARK-1121 Only add avro if the build is for Hadoop 0.23.X and SPARK_YARN is set

Author: Prashant Sharma <prashant.s@imaginea.com>

Closes #6 from ScrapCodes/SPARK-1121/avro-dep-fix and squashes the following commits:

9b29e34 [Prashant Sharma] Review feedback on PR
46ed2ad [Prashant Sharma] SPARK-1121-Only add avro if the build is for Hadoop 0.23.X and SPARK_YARN is set
[SPARK-1089] fix the regression problem on ADD_JARS in 0.9

https://spark-project.atlassian.net/browse/SPARK-1089

copied from JIRA, reported by @ash211

"Using the ADD_JARS environment variable with spark-shell used to add the jar to both the shell and the various workers. Now it only adds to the workers and importing a custom class in the shell is broken.
The workaround is to add custom jars to both ADD_JARS and SPARK_CLASSPATH.
We should fix ADD_JARS so it works properly again.
See various threads on the user list:
https://mail-archives.apache.org/mod_mbox/incubator-spark-user/201402.mbox/%3CCAJbo4neMLiTrnm1XbyqomWmp0m+EUcg4yE-txuRGSVKOb5KLeA@mail.gmail.com%3E
(another one that doesn't appear in the archives yet titled "ADD_JARS not working on 0.9")"

The reason of this bug is two-folds

in the current implementation of SparkILoop.scala, the settings.classpath is not set properly when the process() method is invoked

the weird behaviour of Scala 2.10, (I personally thought it is a bug)

if we simply set value of a PathSettings object (like settings.classpath), the isDefault is not set to true (this is a flag showing if the variable is modified), so it makes the PathResolver loads the default CLASSPATH environment variable value to calculated the path (see https://github.com/scala/scala/blob/2.10.x/src/compiler/scala/tools/util/PathResolver.scala#L215)

what we have to do is to manually make this flag set, (https://github.com/CodingCat/incubator-spark/blob/e3991d97ddc33e77645e4559b13bf78b9e68239a/repl/src/main/scala/org/apache/spark/repl/SparkILoop.scala#L884)

Author: CodingCat <zhunansjtu@gmail.com>

Closes #13 from CodingCat/SPARK-1089 and squashes the following commits:

8af81e7 [CodingCat] impose non-null settings
9aa2125 [CodingCat] code cleaning
ce36676 [CodingCat] code cleaning
e045582 [CodingCat] fix the regression problem on ADD_JARS in 0.9
Show Master status on UI page

For standalone HA mode, A status is useful to identify the current master, already in json format too.

Author: Raymond Liu <raymond.liu@intel.com>

Closes #24 from colorant/status and squashes the following commits:

df630b3 [Raymond Liu] Show Master status on UI page
SPARK 1084.1 (resubmitted)

(Ported from https://github.com/apache/incubator-spark/pull/637 )

Author: Sean Owen <sowen@cloudera.com>

Closes #31 from srowen/SPARK-1084.1 and squashes the following commits:

6c4a32c [Sean Owen] Suppress warnings about legitimate unchecked array creations, or change code to avoid it
f35b833 [Sean Owen] Fix two misc javadoc problems
254e8ef [Sean Owen] Fix one new style error introduced in scaladoc warning commit
5b2fce2 [Sean Owen] Fix scaladoc invocation warning, and enable javac warnings properly, with plugin config updates
007762b [Sean Owen] Remove dead scaladoc links
b8ff8cb [Sean Owen] Replace deprecated Ant <tasks> with <target>
[HOTFIX] Patching maven build after #6 (SPARK-1121).

That patch removed the Maven avro declaration but didn't remove the
actual dependency in core. /cc @scrapcodes

Author: Patrick Wendell <pwendell@gmail.com>

Closes #37 from pwendell/master and squashes the following commits:

0ef3008 [Patrick Wendell] [HOTFIX] Patching maven build after #6 (SPARK-1121).
Removed reference to incubation in Spark user docs.

Author: Reynold Xin <rxin@apache.org>

Closes #2 from rxin/docs and squashes the following commits:

08bbd5f [Reynold Xin] Removed reference to incubation in Spark user docs.
Remote BlockFetchTracker trait

This trait seems to have been created a while ago when there
were multiple implementations; now that there's just one, I think it
makes sense to merge it into the BlockFetcherIterator trait.

Author: Kay Ousterhout <kayousterhout@gmail.com>

Closes #39 from kayousterhout/remove_tracker and squashes the following commits:

8173939 [Kay Ousterhout] Remote BlockFetchTracker.
SPARK-1032. If Yarn app fails before registering, app master stays aroun...

...d long after

This reopens https://github.com/apache/incubator-spark/pull/648 against the new repo.

Author: Sandy Ryza <sandy@cloudera.com>

Closes #28 from sryza/sandy-spark-1032 and squashes the following commits:

5953f50 [Sandy Ryza] SPARK-1032. If Yarn app fails before registering, app master stays around long after
SPARK-1051. On YARN, executors don't doAs submitting user

This reopens https://github.com/apache/incubator-spark/pull/538 against the new repo

Author: Sandy Ryza <sandy@cloudera.com>

Closes #29 from sryza/sandy-spark-1051 and squashes the following commits:

708ce49 [Sandy Ryza] SPARK-1051. doAs submitting user in YARN