Improper tracking of idCounter

[bdemchak]

The idCounter field of metadata is required for all aspects that create IDs (e.g., @id).

The correct value is the largest value of any ID in the aspect, including all previous versions of the aspect.

This is easy enough to calculate by remembering the idCounter that's read from NDEx, knowing the highest @id written to a new version of the aspect, and then taking the max(oldIDCounter, @id). However, this requires that idCounter be saved for all affected aspects that are read.

I don't think this has come up before, but it's useful to get out of the way now.