Add container ID to parameters of creating bucket
Change the term "container" to "bag"

A bag represent a set of riak clusters which are related via MDC repl.
The reason of this change is because the term "container" is used
in Swift.
Don't include bag metadata when request does not have bag information
Refactor types and specs
Use appropriate connection in confirming whether bucket is clean
Merge pull request #76 from basho/feature/multi-cluster-support

Feature/ bag support