[SPARK-1198] Allow pipes tasks to run in different sub-directories

This works as is on Linux/Mac/etc but doesn't cover working on Windows.  In here I use ln -sf for symlinks. Putting this up for comments on that. Do we want to create perhaps some classes for doing shell commands - Linux vs Windows.  Is there some other way we want to do this?   I assume we are still supporting jdk1.6?

Also should I update the Java API for pipes to allow this parameter?

Author: Thomas Graves <tgraves@apache.org>

Closes #128 from tgravescs/SPARK1198 and squashes the following commits:

abc1289 [Thomas Graves] remove extra tag in pom file
ba23fc0 [Thomas Graves] Add support for symlink on windows, remove commons-io usage
da4b221 [Thomas Graves] Merge branch 'master' of https://github.com/tgravescs/spark into SPARK1198
61be271 [Thomas Graves] Fix file name filter
6b783bd [Thomas Graves] style fixes
1ab49ca [Thomas Graves] Add support for running pipe tasks is separate directories
[SQL] Minor fixes.

Author: Michael Armbrust <michael@databricks.com>

Closes #315 from marmbrus/minorFixes and squashes the following commits:

b23a15d [Michael Armbrust] fix scaladoc
11062ac [Michael Armbrust] Fix registering "SELECT *" queries as tables and caching them.  As some tests for this and self-joins.
3997dc9 [Michael Armbrust] Move Row extractor to catalyst.
208bf5e [Michael Armbrust] More idiomatic naming of DSL functions. * subquery => as * for join condition => on, i.e., `r.join(s, condition = 'a == 'b)` =>`r.join(s, on = 'a == 'b)`
87211ce [Michael Armbrust] Correctly handle self joins of in-memory cached tables.
69e195e [Michael Armbrust] Change != to !== in the DSL since != will always translate to != on Any.
01f2dd5 [Michael Armbrust] Correctly assign aliases to tables in SqlParser.
SPARK-1414. Python API for SparkContext.wholeTextFiles

Also clarified comment on each file having to fit in memory

Author: Matei Zaharia <matei@databricks.com>

Closes #327 from mateiz/py-whole-files and squashes the following commits:

9ad64a5 [Matei Zaharia] SPARK-1414. Python API for SparkContext.wholeTextFiles