Table changes scalars in dict to arrays when instantiated

As @zaly found, the kp.Table alters the dict instance (replaces scalars with expanded numpy arrays) when instantiated from it, which might cause unexpected behaviour since the mutation is not explicit. I would consider this being a bug, rather than unexpected behaviour.

This bug is already present for at least two years but was not discovered yet due to the fact that dictionaries are used as throwaway objects, so hopefully this did not cause too much trouble elsewhere.