Rename Null into Uninitialized
bliss.common.utils provides a Null object which is used to deal with uninitialized attributes or vars. Instead of using None, which could be a valid initialized value.
bliss.data.nodes.lima also uses a Unset concept.
I propose to rename it into something a little more explicit.
Use on of this names instead of Null
UninitializedUnset
Let me know, I can take care of the change.