Empty position node in imports

[r0mainK]

So basically when we parse:

import foo
from foo import bar

In both cases, only the uast:RuntimeImport nodes have a position attribute that holds information. The uast:Identifier nodes have a position attribute, but they contains no information. Also, there is only starting information, and nothing about the ending.

I don't know if this is a bug or not, but it would be good if we had positional information propagated through each node, and ending information.