Our understanding of typing.NamedTuple is lossy

[PCManticore]

It seems we can do a much better job over here:

• our current transform is losing the type of the arguments

• we should support typing.NamedTuple subclasses. I just added a basic support for it, but I don't feel it is enough, since we could store the types as well.

• it also seems that NamedTuple can have default values for its attributes

https://docs.python.org/3/library/typing.html#typing.NamedTuple