JCLOUDS-458:Added Blobstore Abstraction

JCLOUDS-458:Added Blobstore Abstraction
Minor Changes testCopyUrl
We need to decide what a project number really means -- it seems to be a subresource of the identity.  While we wire this property through the overrides in `ContextBuilder`, perhaps it makes more sense as part of the identity, similar to what OpenStack does with the its user_id:tenant_id:

http://docs.openstack.org/grizzly/openstack-compute/admin/content/users-and-projects.html

/cc @everett-toews @jdaggett