Juwang-Inserting LoggingScopes

With LoggingScope and LoggingScopeFactory, this PR is to insert LoggingScope in REEF code at major stages to measure the performance. 
This is to resolve issue REEF-28 https://issues.apache.org/jira/i#browse/REEF-28?filter=-1

We need to get the configuration first before creating the injector that is used to inject singleton of LoggingScopeFactory. I have added a static method in LoggingScopeFactory for this case.