Fix issue on initial upload

[btucker]

On initial upload (before cropping), logo_crop_(x|y|w) are all nil. This causes this method to raise an error. Also, there's a missing div with class "update" which prevents the inclusion of the crop partial on the ajax request.

[atd]

I eventually change the classes to add an avatar- prefix and isolete them from the rest of the application

Thank you for your contribution.