Update swift content

I updated the swift content in the installation guide as
follows:

1) Consolidated Identity service configuration into proxy
   service configuration section.
2) Changed initial example architecture to install the proxy
   service on the controller node instead of a separate node.
   However, I used wording that supports separate and/or
   multiple proxy services.
3) The steps to configure memcached break installations with
   horizon because the latter references 127.0.0.1 instead
   of the management network interface IP address. After
   consolidating the proxy service to a single instance on
   the controller node, it now references 127.0.0.1.
4) Changed initial example architecture to install two
   storage nodes rather than five storage nodes to reduce
   the barrier to entry for users that want to try swift.
   However, I used wording that supports additional storage
   nodes and also references the swift documentation for
   larger deployments.
5) Changed the initial example architecture to use only the
   management network instead of a separate storage/replication
   network because the original instructions didn't actually use
   the latter. Fully implementing a separate storage/replication
   network requires a considerably more complex configuration
   and eliminating it reduces the barrier to entry for users
   that want to try swift. However, I used wording that
   mentions a separate storage/replication network and also
   references the swift documentation for larger deployments.
6) The Ubuntu and RHEL/CentOS/Fedora packages include ancient
   upstream/example configuration files that contain
   deprecated/defunct options and lack options that enable
   useful features. Packages take a while to fix, so the
   instructions now pull the upstream configuration files.
7) Removed the steps to create disk labels and partitions on
   the storage nodes because a variety of methods exist and
   users should choose their own method.
8) Changed rsync to run as a standard service rather than use
   the xinetd wrapper on RHEL/CentOS/Fedora.
9) Separated account, container, and object ring creation steps
   into separate sections to improve clarity and reduce typos.
10) Reduced partition power from 18 to 10 during ring creation
    because the example architecture shouldn't scale to the higher
    value using the example architecture.
11) Changed storage node service management steps on Ubuntu to
    use 'swift-init' rather than manually starting a large
    number of services.
12) Modified file names and IDs to increase consistency with
    other content in the guide.

I recommend backporting to Juno as this chapter wasn't
functional in time for release. Also, I'm planning to
improve the diagrams in a future patch.

Change-Id: I26710efe16e8cb6ed1a20ebc70b3f6d5962536d1
Partial-Bug: #1389382
Implements: blueprint installation-guide-improvements
backport: juno
(cherry picked from commit ff5ef1b66a039549671ad99efa1de79fd52fc14e)