Improve the documentation of the config module.

  * Document how to load configurations from file / cli arguments;
  * Deduce None to Opt instead of StrOpt; no visible change.

Change-Id: I9a6b5e02d7ea75ce23fddc36cff85644d2b5f874
Merge "Improve the documentation of the config module."
Message support in WSGI.

  * API limits (on TTL, e.g.) are not verified (noted in code).

Implements: blueprint transport-wsgi

Change-Id: I8c3908ce7e74da26b3ebebd06f308754665d681b
Claim messages in SQlite.

Implements: blueprint storage-reference

Change-Id: Ib10f80e05b169f62885cd1ae88307b9aa3b37c0c
Rename QueueResource to queues.ItemResource.

queues.CollectionResource is not implemented yet.

Change-Id: I8131ce784e0efc5d07a633d93db09d340a6e1281
MessageController implementation for mongodb storage

This patch implements MessageController for the mongodb storage. In
order to test the changes made here, it was necessary to modify current
base classes.

This patch also adds more granular exceptions (QueueDoesNotExist and
MessageDoesNotExist) both based on the existing exception DoesNotExist.

Implements blueprint storage-base
Implements blueprint storage-mongodb

Change-Id: I0752c5d797104a9cc58efd8e866b3b627646bce5
Merge "MessageController implementation for mongodb storage"
Set 'Content-Location' on get-messages correctly.

Change-Id: I9e064d5cdcafdaeb8b9bb92b7b2fa4e557d83aca
Don't call super on queue deletion

This patch removes the super call on queue deletion since it raises
NotImplementedError.

Change-Id: I11f068ff52e99b89c926df9234f9924779c7a941
Merge "Don't call super on queue deletion"