ze'ai'e SE experimental cmavo

selbri conversion: permute all terbri so as to be exactly backward.

For an exactly-n-terbri selbri, it is the (n, n-1, n-2, ..., 2, 1)rd conversion. For zero- or one-terbri selbri, it is trivial (identity - no noticeable change); for one-terbri selbri, this is "re'au'e". For two-terbri selbri, it is equivalent to "se"; it is the 2nd (id est: (2, 1)th) conversion in this case. For a three-terbri selbri, this is equivalent to "te"; it is the 3rd (id est: (3, 1)th) conversion in this case. For four-terbri selbri, it is the (4, 3, 2, 1)rd conversion. For five-terbri selbri, it is the (5, 4, 3, 2, 1)rd conversion.