[Feature Request] Use Clifford to replace Pauli String

[Roger-luo]

Clifford group can be stored by a tableau and be calculated in poly time (on stabilizer states) with either the tableau based algorithm or graph states. A block for Cliffords is more useful when construct/transform/calculate things like graph state, error correction codes.

But since this is deeply related to graph states, this might should go into another package with graph state together.

Related work: Cliffords.jl
FYI: https://arxiv.org/pdf/quant-ph/0602096.pdf