[openstack|storage] add default Accept header
[openstack|storage] add #delete_multiple_objects
[openstack|storage] patch #delete_multiple_objects for Swift v1.8

This commit addresses an issue where the Content-Type header is not
being set correctly in the response. This has been fixed in Swift v1.9.
openstack/swift@ad24cde120efe73fe5a9b866f74c7d3c766aa4cb
[openstack|storage] add methods for SLO support

Adds #put_static_obj_manifest and #delete_static_large_object methods.
[openstack|storage] add #put_dynamic_obj_manifest

Renames the current #put_object_manifest method to better differentiate
this from the new #put_static_obj_manifest method. #put_object_manifest
has been retained for backward compatibility.
[openstack|storage] patch #delete_static_large_object for Swift v1.8

This commit addresses an issue where the Content-Type header is not
being set correctly in the response. This has been fixed in Swift v1.9.
openstack/swift@ad24cde120efe73fe5a9b866f74c7d3c766aa4cb
Merge pull request #2191 from burns/openstack_bulk_delete_slo

[openstack|storage] add bulk delete and SLO support