Shuffle Performance fix: Use netty embeded OIO file server instead of ConnectionManager
Shuffle Performance Optimization: do not send 0-byte block requests to reduce network messages
change reference from io.Source to scala.io.Source to avoid looking into io.netty package

Signed-off-by: shane-huang <shengsheng.huang@intel.com>
fix a bug in netty Block Fetcher

Signed-off-by: shane-huang <shengsheng.huang@intel.com>
first attempt at an RDD to pull data from JDBC sources
prevent mysql driver from pulling entire resultset into memory. explicitly close resultset and statement.
Added a BlockObjectWriter interface in block manager so ShuffleMapTask
doesn't need to build up an array buffer for each shuffle bucket.
Allow changing the serializer on a per shuffle basis.
Allow the specification of a shuffle serializer in the read path (for
local block reads).
Merge branch 'blockmanager' of github.com:rxin/spark into blockmanager

Conflicts:
	core/src/main/scala/spark/storage/DiskStore.scala
Merge branch 'master' of github.com:mesos/spark into blockmanager
Added a shuffle block manager so it is easier in the future to
consolidate shuffle output files.
Allow specifying the shuffle write file buffer size. The default buffer
size is 8KB in FastBufferedOutputStream, which is too small and would
cause a lot of disk seeks.
Merge branch 'master' of github.com:mesos/spark into blockmanager

Conflicts:
	core/src/main/scala/spark/BlockStoreShuffleFetcher.scala
Two minor fixes according to Ryan LeCompte's review.
a) Add support for hyper local scheduling - specific to a host + port - before trying host local scheduling.

b) Add some fixes to test code to ensure it passes (and fixes some other issues).

c) Fix bug in task scheduling which incorrectly used availableCores instead of all cores on the node.
Fix some npe introduced accidentally
Merged Ram's commit on removing RDDs.

Conflicts:
	core/src/main/scala/spark/SparkContext.scala
Cleaned up Ram's code. Moved SparkContext.remove to RDD.unpersist.

Also updated unit tests to make sure they are properly testing for
concurrency.
Added SparkContext.cleanup back. Not sure why it was removed before ...
Changed the type of the persistentRdds hashmap back to
TimeStampedHashMap.
Integrate review comments on pull request