Moving nested 'storage.acl.ACL.Entity' to module scope.
Support marshalling lists to value_pb.list_value.

Closes #223.  (again).
Merge pull request #265 from tseaver/223-marshal_list_values

Finish #223:  Support marshalling lists to 'value_pb.list_value'
Remove 'Connection.delete_entity' API.

Fixes #169.
Return True from 'Connection.delete_entities' unconditionally.

Fixes #168.

Merges 169-connection_delete_entity, too.
Merge pull request #257 from tseaver/168_169-connection_delete_entities

Fix #168 and #169:  Rationalize 'Connection.delete_entities'
Merge pull request #264 from dhermes/remove-nested-class-def

Moving nested 'storage.acl.ACL.Entity' to module scope.
Refactoring duplicate code between storage.key and storage.bucket.