i think the options without xy are not valid, as some bundles need base
paths to other documents as well. i would be happy with xy_basepath but
then we need to change this config to basepath. xy_base_path is ok too,
but not sure if its worth the BC break. then again when we move the
paths to the phpcr specific configuration section, we have a BC break
anyways, so chose what you think is the cleanest.