new version of go-restful handles flat / gzip encoding in the Container
redis.AddFlat is meaningless as it uses fmt.Print(#v)

Therefore it is required to use an intermediate represenation of flat values
and manually convert between types. By doing so, an array can be
JSON-encoded, serlialised and written to redis. Afterwards this value can
be Marshaled to a []string, which would otherwise be imposible using redis.AddFlat
new functionality: Add DateSets based on their taxonomy membership