UN-UNTOUCHED

removed UNTOUCHED constant, to avoid recuring confusion

assigned to @palmb

changed title from removed UNTOUCHED constant, to avoid recuring confusion to UN-UNTOUCHED

changed the description

added accepted category: (global) constants category: public API cleanup/refactoring labels

requested review from @schaefed

I already had this change prepared yesterday and then decided against it. Using np.nan alongside the constants UNFLAGGED and BAD` also felt confusing to me. But I don't mind merging this anyhow.

approved this merge request

merged

mentioned in commit 670aa8e7