Flag taxa without descendants

[DianRHR]

It is important to have a clear idea of how many taxa (orders and families to start) are there in the COL and the xRelease without descendants to direct the search for datasets that potentially fill those gaps.

We should flag those names that have no descendants as descendants mising and it could be following these premises:

1. rank: above genus
2. status: accepted or provisionally accepted
3. its id is not included as the "parentID" of any lower-ranking taxon