Made changes to the SparkContext to have a DynamicVariable for setting local properties that can be passed down the stack. Added an implementation of the fair scheduler
Changed the name of the system property to set the allocation xml
Updated/Refactored the Fair Task Scheduler. It does not inherit ClusterScheduler anymore. Rather, ClusterScheduler internally uses TaskSetQueuesManager that handles the scheduling of taskset queues. This is the class that should be extended to support other scheduling policies
Cleaned up the code
Removed some commented code
refactor fair scheduler implementation
1.Chage "pool" properties to be the memeber of ActiveJob
2.Abstract the Schedulable of Pool and TaskSetManager
3.Abstract the FIFO and FS comparator algorithm
4.Miscellaneous changing of class define and construction
Just update typo and comments
1.remove redundant spacing in source code
2.replace get/set functions with val and var defination
change some typo and some spacing
add properties default value null to fix sbt/sbt test errors
Contiue to update codes for scala code style
1.refactor braces for "class" "if" "while" "for" "match"
2.make code lines less than 100
3.refactor class parameter and extends defination
refactor the Schedulable interface and add unit test for SchedulingAlgorithm
remove TaskSetQueueManager and update code style
when akka starts, use akkas default classloader (current thread)
use threads classloader when deserializing task results; classnotfoundexception includes classloader
Fix ClusterScheduler bug to avoid allocating tasks to same slave
expose TaskSetManager type to resourceOffer function in ClusterScheduler
Merge branch 'master' into xiajunluan

Conflicts:
	core/src/main/scala/spark/SparkContext.scala
	core/src/main/scala/spark/scheduler/cluster/ClusterScheduler.scala
	core/src/main/scala/spark/scheduler/cluster/TaskSetManager.scala
fix bug of unit tests
fix CheckpointRDD getPreferredLocations java.io.FileNotFoundException