Support using the last value of multi-valued filenameTags in DirectoryStorageService #22
Description
Related to #21, I would welcome if filenameTag in DirectoryStorageService could be extended to support indexing of multi-valued tags such as ImageType. For example, I would like to use filenameTag="ImageType[end]" instead of filenameTag="ImageType" to get NORM instead of DERIVED_PET_NORM.