added methods to get lists of objects

The following methods were added (for the file storage):

listTags(const std::string &name, int size, int page, const std::string &sort) listGlobalTags(const std::string &name, int size, int page, const std::string &sort) findGlobalTagMap(const std::string &name, const std::string &xCrestMapMode) selectIovs(const std::string &name, long since, long until, long snapshot, int size, int page, const std::string &sort)