Implement Parent/Child Support

[polyfractal]

Should detect when a parent or child is being queried (e.g. when using has_child, etc), or when trying to to query a field that is mapped as a child.

By detecting this relationship, highlighting can be autodetected (as well as type-checking the relationship)

[stof]

The curl command generated to explain a result also need to support parent/child relationship when explaining a match on the child type