update SLO delete error handling

* ensure all responses are 200 OK
* report missing sub-SLO manifests or other error messages in bulk
  delete response

Change-Id: Iaf88c94bc7114ff3c9751f9f31f8f748de911f8a
Update SAIO doc to have double proxy-logging in pipeline.

Change-Id: I0a034ca1420761cbf4e35dcea1d9cd18a92f90bd
Install libffi-dev in SAIO docs.

If you don't, then newer versions of xattr won't install, and since
our xattr requirement is simply ">= 0.4" in requirements.txt, this
affects anyone setting up a new SAIO.

This happened with xattr 0.7, which was released on 2013-07-19.

Change-Id: Iaf335fa25a2908953d1fd218158ebedf5d01cc27
Merge "update SLO delete error handling"
Fix internal swift.source tracking.

In 1.8.0 (Grizzly), your proxy logs would indicate which middleware
was responsible for an internal request, e.g. TU for tempurl or BD for
bulk delete. At some point, those all turned into GET_INFO, which does
not give you any idea which specific middleware was responsible, only
that it came from a get_account_info/get_container_info call.

This commit puts it back to how it was in 1.8.0. Also, the
new-since-1.8.0 function get_object_info() got swift_source plumbing
added to it, so source tracking for the quota middlewares'
get_object_info() calls will happen now too.

Note that due to the new-since-1.8.0 in-environment caching of
account/container info, you may not see as many lines in the proxy log
as you would with 1.8.0. This is because there are actually fewer
internal requests being made.

Change-Id: I2b2ff7823c612dc7ed7f268da979c4500bbbe911
Merge "Update SAIO doc to have double proxy-logging in pipeline."
bulk delete bug with trailing whitespace

Change-Id: Ia48224a1a187a8ed6b0c9a3c72cac06f084a6fc8
improve bulk document

This a very small change which just tell users request url of bulk
delete request. In original docstrings, it just states the request
parameters, request body and request method but not request url.

Change-Id: I0bbc302a0e072910bb58e4814614d7f761433b10
Merge "Install libffi-dev in SAIO docs."
Merge "bulk delete bug with trailing whitespace"