Build metrics system framwork
Add Master and Worker instrumentation support
Update metric source support for instrumentation
MetricsSystem refactor
refactor metrics system
1.change source abstract class to support MetricRegistry
2.change master/work/jvm source class
Code clean and remarshal
Add dependency of Codahale's metrics library
Add Executor instrumentation
Add default properties to deal with no configure file situation
Add metrics system unit test
Remove twice add Source bug and code clean
Add metrics source of DAGScheduler and blockManager

Conflicts:

	core/src/main/scala/spark/SparkContext.scala
	core/src/main/scala/spark/SparkEnv.scala
Refactor metricsSystem unit test, add resource files.
Register and init metricsSystem in SparkContext

Conflicts:

	core/src/main/scala/spark/SparkContext.scala
	core/src/main/scala/spark/SparkEnv.scala
Change Executor MetricsSystem initialize code to SparkEnv
Add Maven metrics library dependency and code changes
Fix some typos
continue to refactor code style and functions
Add metrics config template file
Change class xxxInstrumentation to class xxxSource