Rename display_parent_relation to display_allocations

[ewuerger]

Basically the title.

[huyenngn]

Since the display_parent_relation flag defaults to True for all model elements now, consider changing the name to hide_parent_relation/hide_allocations, which defaults to False. Having flags default to True seems counterintuitive, as it might be confusing to explicitly set a flag and not have it change anything.