Support alt and title fields for File Entity module

The module provides an option for alt and title values when using File Entity, but no token values are rendered. This is due to the File Entity module having their own fields for alt and title, known as field_file_image_alt_text and field_file_image_title_text, respectively.

The attached patch includes additional code to handle the case where File Entity is in use and the alt/title fields are present. Please review, thanks.