Clarify Swift's implementation definition in the Install Guide page

The current definition of Swift's implementation in the Install
Guide page is confusing and, therefore, incomplete. The root of
the confusion is as it follows: "Its implementation is not like
a file server with mountable directories.", which doesn't
actually explain what it is like. Clarify this concept adding
information about Swift's implementation.

Patch Set 2: Rewording of paragraph.
Patch Set 3: Small adjustment regarding grammar issues.

Change-Id: I9bca8bd1df758e5de1201231efb3c245f1cfe9a4
Closes-Bug: #1412456

doc/common/ch_getstart.xml

@@ -89,10 +89,12 @@
                 </td>
                 <td>Stores and retrieves arbitrary unstructured
                     data objects via a <glossterm>RESTful</glossterm>,
-                    HTTP based API. It is highly
-                    fault tolerant with its data replication and scale out
-                    architecture. Its implementation is not like a file server
-                    with mountable directories.</td>
+                    HTTP based API. It is highly fault tolerant with
+                    its data replication and scale-out architecture.
+                    Its implementation is not like a file server with
+                    mountable directories. In this case, it writes
+                    objects and files to multiple drives, ensuring the
+                    data is replicated across a server cluster.</td>
             </tr>
             <tr>
                 <td><link