dev-manual: Updated manual overview to include new QEMU chapter

Fixes [YOCTO #641]

Added a new bullet to the list that overviews what the manual
covers.

(From yocto-docs rev: 54bdb50df3951346a2e926700681db55bd59a2e1)

Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/dev-manual/dev-manual-intro.xml

@@ -67,6 +67,11 @@
                     generally used during image development for
                     embedded devices.
                     </para></listitem>
+                <listitem><para>Information on using the Yocto Project
+                    integration of the QuickEMUlator (QEMU), which lets you
+                    simulate running on hardware an image you have built using
+                    the OpenEmbedded build system.
+                    </para></listitem>
                 <listitem><para>Many references to other sources of related
                     information.</para></listitem>
             </itemizedlist>