Removed all usage of ConfigurationFile and replaced it with ConfigurationSerializer
Updates according to code review
 * Updated YarnContainerManager to use ConfigurationSerializer.
 * Deleted FileUtils, as YarnContainerManager was the only user left
Merge branch 'master' of https://github.com/Microsoft-CISL/REEF into weimer_remove_configurationFile
Merge pull request #723 from Microsoft-CISL/weimer_remove_configurationFile

Removed all usage of ConfigurationFile