Steve/instance aggregation

[StevenBorkman]

Modified instance segmentation labeler to support aggregating children into a parent's instance segmentation result. This capability is built on changes made recently to labeling to support hierarchical label definitions. Now when a user requests to aggregate the results, all of the sub-components will be considered the same instance of an object. If a user selects to not aggregate their results, then each sub-component will be considered a distinct instance of an object.