unique=True for booleanBones

[phneutral]

Hey guys,

recently I stubbled upon a use-case for unique booleanBones. At the moment you can't use unique in combination with boolean, because you can create exactly two entries (one True, the other False) and after that you can't load the skeleton at all — it will result in Error 500. What would it be like if boolean unique=True would only refer to True? You could highlight a special entry like this.