Have the riak store create bucket types in create_schema

[cabol]

Currently the riak store create_schema does not fulfill its responsibility of preparing the storage for the data. The bucket type creation and activation, index creation and association to the bucket must be done manually through the riak-admin command and riak's REST API.

It would be preferable to handle this automatically, possibly tuning it via create_schema option parameters.

NOTE: This issue was moved here from the original inaka/sumo_db#145