InterGraphDataSource/Sink commented, ConstantDataSource extented with an empty constructor.
InterGraphDataSource/Sink commented, ConstantDataSource extented with an empty constructor.

MicrosoftResearch/Naiad,TimelyDataflow/Naiad,ms705/Naiad,ms705/Naiad,TimelyDataflow/Naiad,MicrosoftResearch/Naiad,xinhaoyuan/Naiad,xinhaoyuan/Naiad