expose RDD & storage info directly via SparkContext
better formatting for RDDInfo
Merge branch 'master' into blockmanager_info
rename Slaves --> Executor
Merge branch 'master' into blockmanager_info

Conflicts:
	core/src/main/scala/spark/storage/BlockManagerMaster.scala
fixup merge (master -> driver renaming)
track total partitions, in addition to cached partitions; use scala string formatting
remove unneeded (and unused) filter on block info
Merge pull request #422 from squito/blockmanager_info

RDDInfo available from SparkContext