Change behaviour of original bounds for Binary variables

[davidggphy]

In Binary variables, if the inputs lowBound and upBound are the default None values, in the __init__ the self.lowBound and self.upBound are set to 0,1. But the self._lowbound_original, self._upbound_original are set to None. In the rest of the variables (Continuous, Integer) these two pairs of attributes coincide.

This is, the behaviour is equivalent to

self.lowBound = 0
self.upBound = 1
self._lowbound_original = None
self._upbound_original = None

It seems more consistent to have

self.lowBound = self._lowbound_original = 0
self.upBound = self._upbound_original  = 1

closes #620

[davidggphy]

Looks like this behaviour breaks something, but just in the macOS version 3.10.