Refactor txaws.storage to match the recent work in txaws.ec2

[Duncan McGreggor]

In the EC2 code, we have a client and a query object that is used with the client:
 * txaws.ec2.client.EC2Client
 * txaws.ec2.client.Query

In the S3 code, we should maintain a symmetry here, and thus do the following:
 * rename txaws.storage.client.S3Request -> Query
 * rename txaws.storage.client.S3 -> S3Client
 * find common code between txaws.ec2 and txaws.storage, and if there is any, factor that out to a txaws.query.Query class

Docs:
 * http://docs.amazonwebservices.com/AmazonS3/latest/
 * http://docs.amazonwebservices.com/AmazonS3/2006-03-01/API/index.html

[Duncan McGreggor (oubiwann)]

The refactor is complete, now. The next step is checking the new code against Amazon's service.

[Duncan McGreggor (oubiwann)]

Excellent! I've checked that all the currently supported features in txaws.s3 are working against Amazon (this required some fixes). I've pushed the changes and will do a pre-review, and then submit for review :-)

[Duncan McGreggor (oubiwann)]

Ready for review...

[Duncan McGreggor (oubiwann)]

  Merged 474353-storage-ec2-symmetry [r=lifeless] [f=474353]

  This change brought the storage subpackage (now renamed to s3) up to date with
  the ec2 subpackage (style, unit tests, idioms, error handling). This work
  included factoring out common code between ec2 and s3 and putting it in the
  base client.