Added features_override module as dependency.
Updated ting_visual_relation_get_recommendations. If the ADHL-service returns an empty array, try once more.
Added d3 module as depency.
Added features_override module in make-file.
Updated ting_visual_relation_get_cover_url(). Changed variable name to make it more consitent.
Added ting_visual_relation_get_default_cover helper function and updated ting_visual_relation_get_ting_object() to include a default cover if nothing was found using the addi-service.