Attributes

This branch introduces a framework for automatic attribute annotation using information provided by Turk labelers.
I sort of remember what was going on here: at one stage of this branch I was storing both the regressed attributes and the ground truth in a single map within a file.  Thus, those variables were present src and were not overwritten with the new variable containing the regressed value when the fork merged (@caotto, you're exactly right).  It looks like at some point, that logic was changed because I don't see it in this diff.  Thus, this probably can be reverted.