Add userID Attribute

[kdottiemo]

After discussing among ourselves and with Chip, we've realized that one way in which the polygon attributes could be enhanced is with the addition of "userID" as an automatic attribute. This could potentially be pulled from the home string of the user. ("C:\Users..."), which we get anyway in the appdata path. That way, the user could refine a search, looking for shapes drawn only by a certain person (or at least from a certain machine.)