Applying the OROperator with an empty outputSpace to represent zeroOrOne

[dany-fu]

Expected: two edges between two nodes
Actual: one edge

This can be reproduced on the current combinatorial_sbol branch

constellation_optional_one.txt

[nroehner]

Please see my recent commit

ffd6bc0.

I think this fixes the issue by a adding nodespace with blank edge to the list of input spaces when applyOperator is called with the zero-or-one operator.