Added indexOf to SafeSeqsConstraint, and use it in Every and sIndexOf in SafeSeqs.
Added lastIndexOf to SafeSeqsConstraint, and use it in Every and sLastIndexOf in SafeSeqs.
Added indexOfSlice to SafeSeqsConstraint, and use it in Every and sIndexOfSlice in SafeSeqs.
Added lastIndexOfSlice to SafeSeqsConstraint, and use it in Every and sLastIndexOfSlice in SafeSeqs.