SPARK-1024 Remove "-XX:+UseCompressedStrings" option from tuning guide

remove "-XX:+UseCompressedStrings" option from tuning guide since jdk7 no longer supports this.

Clarify that Python 2.7 is only needed for MLlib

Workers should use working directory as spark home if it's not specified

If users don't set SPARK_HOME in their environment file when launching an application, the standalone cluster should default to the spark home of the worker.

Made some classes private[stremaing] and deprecated a method in JavaStreamingContext.

Classes `RawTextHelper`, `RawTextSender` and `RateLimitedOutputStream` are not useful in the streaming API. There are not used by the core functionality and was there as a support classes for an obscure example. One of the classes is RawTextSender has a main function which can be executed using bin/spark-class even if it is made private[streaming]. In future, I will probably completely remove these classes. For the time being, I am just converting them to private[streaming].

Accessing underlying JavaSparkContext in JavaStreamingContext was through `JavaStreamingContext.sc` . This is deprecated and preferred method is `JavaStreamingContext.sparkContext` to keep it consistent with the `StreamingContext.sparkContext`.

GraphX shouldn't list Spark as provided.

I noticed this when building an application against GraphX to audit the released artifacts.

Updated Debian packaging

More yarn code refactor

Try to retrive common code in yarn alpha/stable for  client and workerRunnable to reduce duplicated codes. By put them into a trait in common dir and extends with them.

Same works could be done for the remaining files in alpha/stable , while the remainning files have much more overlapping codes with different API call here and there within functions, and will need much more close review , aslo it might divide functions into too small trifle ones, thus might not deserve to be done in this way.

So just make it run for these two files firstly.

remove "-XX:+UseCompressedStrings" option from tuning guide since jdk7 no longer supports this.

Rename VertexID -> VertexId in GraphX

Fixed the flaky tests by making SparkConf not serializable

SparkConf was being serialized with CoGroupedRDD and Aggregator, which somehow caused OptionalJavaException while being deserialized as part of a ShuffleMapTask. SparkConf should not even be serializable (according to conversation with Matei). This change fixes that.

@mateiz @pwendell

Fixed SVDPlusPlusSuite in Maven build.

This should go into 0.9.0 also.

Changed SparkConf to not be serializable. And also fixed unit-test log paths in log4j.properties of external modules.

Additional edits for clarity in the graphx programming guide.

Added an overview of the Graph and GraphOps functions and fixed numerous typos.

Describe caching and uncaching in GraphX programming guide

Don't clone records for text files

Add GraphX dependency to examples/pom.xml

Deprecate rather than remove old combineValuesByKey function

API doc update & make Broadcast public

In #413 Broadcast was mistakenly made private[spark]. I changed it to public again. Also exposing id in public given the R frontend requires that.

Copied some of the documentation from the programming guide to API Doc for Broadcast and Accumulator.

This should be cherry picked into branch-0.9 as well for 0.9.0 release.

Maintain Serializable API compatibility by reverting back to java.io.Serializable for Broadcast and Accumulator.

Note that previously Broadcast class was accidentally marked as private[spark]. It needs to be public
for broadcast variables to work. Also exposing the broadcast varaible id.