Blockstorage behaviors refactor and versioning
* Implemented exception-raising behaviors for volumes_api.
* Removed blockstorage provider.
* Added volume and snapshot statuses model.
* Refactored response models.
* Versioned volumes_api as v1, added stub for v2
* Cleaned up rax auth extensions
* Fixed VolumeTypeList model
* Added default_volume_type config property

Change-Id: I706fb867e9d892dceb994eeb9052d45d9c649fbf