I changed the implementation locally to use a catchall. Here is the result of running my previous example, i think the error message is sufficient. Thoughts?

```
$ dev/dev1/bin/riak-admin bucket-type create crdt5 '{"props": {"datatype": "set", "allow_mult": "abc"}}'                                                                                                                                rdb-bucket-type-validator/riak | develop
Error creating bucket type crdt5: [{allow_mult,
                                       "Data Type buckets must be allow_mult=true"}]
```