Add BucketType to front-end.

For consistency's sake and to prevent too many defensive 'None'
checks, I've assumed that if a bucket is a traditional type-less
bucket, that its bucket-type is 'default'. The transports can deal
with default vs. non-default on behalf of the user.
Add client operations for get/set bucket type props.
Add feature detection for bucket types.
Add stubs for get/set bucket-type props in transport.
Plumb in the bucket type props requests
Add bucket types to existing requests
Fix documentation copy-pasta
Change the repr format of bucket[-type]s
Fix PEP8 warnings
Fix pyflakes warnings in PB transport
Fix pyflakes error in client ops
misc bucket types test fixes