Enables parenthesis evaluation

@BrettASwift @kadst43 Had it mostly working before... instituting the graph failure check made this a lot easier. Still should have a few people mess with it a bit.
This needs to be a string. `-``-2` is evaluating to 2 which is multiplying with variables. We need to keep the subtraction. `"- (" + argument0 + ")"` should work.