FIX:annotation semantics: adresses #1283

I followed the logic of the discussion in #1283: changed the names of read_annot write_annot to match the pattern we established. I also changed _read_annot to read_annot (and did the same for _write_annot).
why

read_annot_labels
write_labels_annot

and not:

read_annot_labels
write_annot_labels

? would be more consistent