Add copy method to Options

[chriseclectic]

Summary

Adds copy method to the Option class.

Details and comments

The option refactor changes the behaviour of copy.copy(opts) compared to the original class so that changing option values of the copy also change the original.

This adds a copy method for returning a shallow copy of option values where changes of the copy do not change the values of the original.

This copy functionality is used in qiskit-experiments.

[coveralls]

Pull Request Test Coverage Report for Build 1544592361

• 4 of 4 (100.0%) changed or added relevant lines in 1 file are covered.
• 5 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.007%) to 83.092%

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Files with Coverage Reduction	New Missed Lines	%
qiskit/extensions/quantum_initializer/uc.py	2	88.65%
qiskit/pulse/library/waveform.py	3	89.36%

Totals
Change from base Build 1537608485:	-0.007%
Covered Lines:	51663
Relevant Lines:	62176

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💛 - Coveralls

[levbishop]

Did you consider defining __copy__() with the desired behaviour?

[chriseclectic]

@levbishop Yes, but @jakelishman was strongly against adding that method and said to add a copy instead.

[jakelishman]

I read the spec again, and I think I was wrong the first time. I think for what we are, we should implement this method as __copy__ instead. However, if we're calling __setstate__ like this to do the copy, the output type should be constructed only from its __new__, not its __init__

[mtreinish]

LGTM