DocMgmt odata endpoint should support structure/descendants expansion

[awei3]

The Legacy REST interface enabled descendant expansion of WTDocuments with structure, but the new odata interfaces do not have an accommodation for this. We're using APIs to access WTDocuments to implement process ecosystems, thus the odata changeover has been problematic.

The /descendants call in WRS 1.6 and 1.7 seems to still return structure data, but are missing some parameters we expected from WRS 1.5. Right now we are using a hybrid approach of using /descendants to acquire structure, and odata to acquire parameters, but an integrated approach using pure odata would be preferred.