HttpServeShellCmdtHandler and http server changes

Adding HttpServeShellCmdtHandler to handle  Distributed Shell Command
Moving CommandUtility from reef-websever to helloHttp to share it with
ShellTask
HelloDriver to have all the event handlers
Remove helloTask
Merge branch 'master' of https://github.com/Microsoft-CISL/REEF into juwang-httpServerDistributedShell
Merge branch 'master' of https://github.com/Microsoft-CISL/REEF into juwang-httpServerDistributedShell
DriverServiceCOnfiguration
Move command utility to common
Use DriverServiceConfiguration
Update HttpServer/JettyHandler
Fixing locality issue

There was a data locality bug because I was using eval ids instead of
hostnames. The dfs blocks have host names. Fixing that.
Merge pull request #806 from Microsoft-CISL/shravan_dataloading_locality

Fixing locality issue
Updated wake and tang to 0.4
[maven-release-plugin] prepare release reef-project-0.4
[maven-release-plugin] prepare for next development iteration
Updated wake and tang dependencies to 0.5-SNAPSHOT
Refactor adn clean up
Merged from master
merge from master
Removed some left-over files. They have been deleted earlier, but their licensing headers re-appeared, probably as part of a botched PR.
Close the parent context in DefaultContextClosureHandler
The addresses #810 by closing the parent context in `DefaultContextClosureHandler`, if there is any.
Merge pull request #811 from Microsoft-CISL/weimer_810

Close the parent context in DefaultContextClosureHandler
Merge branch 'master' of https://github.com/Microsoft-CISL/REEF into juwang-httpServerDistributedShell
Update for review comments