Make gate_sets actually optional

[dstrain115]

• mypy and pycharm need a default value in the abstract interface
  in order to be truly optional.
• Also, add a copy of the inherited arguments in
  SimulatedLocalProcessor.

[MichaelBroughton]

All of the changes here look like dangerous default values. Would it be possible for the optional case to do something like:

def my_method(some_optional_thing = None):
   if some_optional_thing is None:
    some_optional_thing = promote_to(somethingorother)

?

[dstrain115]

All of the changes here look like dangerous default values. Would it be possible for the optional case to do something like:

Changed.

[mpharrigan]

what about get_sampler

[mpharrigan]

oh weird maybe I was looking at only a subset of commits