Add more quantum gates

Add the following quantum gates

• sqrtnot
• snot
• sign
• berkeley
• cswap
• iswap
• sqrtswap
• sqrtiswap
• fredkin

New gates from Qiskit

• c3x 3-qubit controlled X gate
• c3sx 3-qubit controlled sqrt-X gate
• c4x 4-qubit controlled X gate
• dcx double CNOT gate
• ch controlled Hadamard gate
• ms MS gate
• rxx RXX gate
• ryy RYY gate
• rzz RZZ gate
• rzx RZX gate

Please add more gates that you find interesting to be implemented.