objects are now densely saved in a sorted vector (id = index) and therefore can be accessed directly by the table
subojects now store objects id instead of references since vector refs are invalidated often
on changes only one row in the table is updated (the selection mechanism sometimes still resets the selection data)
because of that the table is now sortable (not too slow anymore) with working selection
the subobject vector inside each object is now sorted too which simplifies merging
all these changes significantly increase performance of all the segmentation functionality