Add File Archiving section to Data Storage page.

It's short, since we don't have support for it at the moment, but it'd
be nice to have actual documentation rather than just the FAQ.

Change-Id: Ia1190567db085421f67c36dee49c692f0330c089
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>

doc/src/datastorage.qdoc

@@ -262,4 +262,15 @@ qrc scheme.
 \list
 \li \l {The Qt Resource System}
 \endlist
+
+\section1 File Archiving
+
+An archive file is a collection of files or directories which are generally
+compressed in order to reduce the space they would otherwise consume on a
+drive. Examples of archive files are ZIP, TAR, RAR and 7z.
+
+Qt has support for archives produced by zlib (see
+\l{How to compress data with Qt?}{qCompress() and qUncompress()}). There are
+also several \l{Add-ons}{3rd party libraries} which can be used.
+
 */

doc/src/external-resources.qdoc

@@ -64,3 +64,13 @@
     \externalpage http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html
     \title GNU Lesser General Public License, version 2.1
 */
+
+/*!
+    \externalpage http://qt-project.org/faq/answer/how_to_compress_data_with_qt
+    \title How to compress data with Qt?
+*/
+
+/*!
+    \externalpage http://qt-project.org/wiki/Category:Add-ons
+    \title Add-ons
+*/