Add reset to standard_gate_instruction

[chriseclectic]

Summary

This extends errorutils.standard_gate_instruction to convert single-qubit reset Kraus operations to standard qobj reset instructions.

Details and comments

Example:
kraus reset to 0 or 1:

reset0 = {'name': 'kraus', 'qubits': [0], 'params': [array([[1, 0], [0, 0]]), array([[0, 1], [0, 0]])]}
reset1 =  {'name': 'kraus', 'qubits': [0], 'params': [array([[0, 0], [0, 1]]), array([[0, 0], [1, 0]])]}

Then the modified instruction can convert these as:

standard_gate_instruction(reset0) -> [{'name': 'reset', 'qubits': [0]}]
standard_gate_instruction(reset1) -> [{'name': 'reset', 'qubits': [0]}, {'name': 'x', 'qubits': [0]}]

Note that the comparison is done using the SuperOp representation so any Kraus representation equivalent to the reset will be converted, not just the canonical ones.