SafeSeqsConstraint Enhancement

-Added indexOf, lastIndexOf, indexOfSlice, and lastIndexOfSlice methods on SafeSeqsConstraint.
-Make Every to use the enhanced version of SafeSeqsConstraint's indexOf, lastIndexOf, indexOfSlice, and lastIndexOfSlice.
-Added sIndexOf, sLastIndexOf, sIndexOfSlice, and sLastIndexOfSlice methods to SafeSeqs.