Support fetching and building Hive and Shark (initial attempt).

Main additions/refactorings:
* Added 'SPARK' and 'SHARK' prefixes and modifiers to relevant variables in
  config.py.template.
* Moved a block of execution code in bin/run to a new run_tests() so that the
  method can be used to execute each group of tests (e.g all tests in
  config.SPARK_TESTS).
Add generated Shark and Hive components to '.gitignore'.
If Shark or Hive preparation should be skipped, check that respective
directories exist in the perf-test project directory.

Modifications (+ some minor refactoring) added to 'bin/run'.
Add a new TestRunner in shark.perf package.

The main() initializes SharkEnv and SharkContext, but does not yet support
PerfTest runs.
Use Java's 'user.dir' system property to find the project directory in
spark.perf.TestRunner#main().

Also includes other minor refactoring in the TestRunner and PerfTest.
Initial attempt at modifying build.sbt to include Shark and Hive assembly.
Misc additions (e.g. the test-warehouses dir) and comments in '.gitignore'.
Print the number of tests executed for each group.
Fix bug in run_tests(). It was still hardcoded to run config.SPARK_TESTS.
Prepend path to jar for Hive builtin functions to the classpath used for config.SCALA_CMD.

See comment in code for an explanation. This gets shark.perf.TestRunner#main() running!
For now, comment out all Shark tests except for table scan.

They are not yet implemented :(
Don't filter everything in META-INF during assembly.
"scan-query" => "table-scan-query".

shark.perf.TestRunner still missing functionality.
Add support for setting up Hive and Shark.

Conflicts:
	bin/run
	config/config.py.template
	src/main/scala/spark/perf/PerfTest.scala
Some small comment edits and deleted extra newline.
Fix PerfTest merge mistake.
Make all Spark/Shark config flags have "SPARK_"/"SHARK_" prefixes
Don't build/run Spark/Shark perf tests if config.SHARK_TESTS is empty.

This also gets rid of double-negatives in 'if' conditions in the run script.

To get the code to compile, cleared spark/work directory before building perf tests.
That directory might contain the perf-test-assembly.jar, which causes issues
with subsequent calls of 'sbt clean assembly'
Put Spark Shark pert tests into separate directories, each with its own sbt settings and assembly.
Rephrase comment with a double negative...