Make TaskRuntime runnable instead of inheriting from Thread; other
cosmetic fixes
Merge branch 'master' into sergiym_task_runtime_thread
Merge branch 'master' of github.com:Microsoft-CISL/REEF into sergiym_task_runtime_thread
Merge branch 'master' into sergiym_task_runtime_thread
move Thread object from TaskRuntime to ContextRuntime
bug: do not use task state in teh ID
Merge pull request #889 from Microsoft-CISL/sergiym_task_runtime_thread

Make TaskRuntime implement Runnable interface; move Thread to ContextRuntime