Starvation check in ClusterScheduler
Starvation check in Standlone scheduler
Changing to use Timer based on code review
Minor fixes
Merge remote-tracking branch 'pwendell/starvation-check'

Also fixed a bug where master was offering executors on dead workers

Conflicts:
	core/src/main/scala/spark/deploy/master/Master.scala
Several fixes to the work to log when no resources can be used by a job.

Fixed some of the messages as well as code style.