documentation/poky-ref-manual: Changed top-level titles

Each of these chapters needed the title changes to reflect Yocto
Project and not Poky.

(From yocto-docs rev: a6d8d01b20af334ca9950c4287d61a728532f652)

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

documentation/poky-ref-manual/development.xml

@@ -2,7 +2,7 @@
 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
 
 <chapter id="platdev">
-<title>Platform Development with Poky</title>
+<title>Platform Development with the Yocto Project</title>
 
     <section id="platdev-appdev">
     <title>Application Development Using the Yocto Project</title>

documentation/poky-ref-manual/extendpoky.xml

@@ -3,7 +3,7 @@
 
 <chapter id='extendpoky'>
 
-<title>Extending Poky</title>
+<title>Extending the Yocto Project</title>
     <para>
         This chapter provides information about how to extend the functionality
         already present in Poky.

documentation/poky-ref-manual/usingpoky.xml

@@ -1,7 +1,7 @@
 <!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
 <chapter id='usingpoky'>
-<title>Using Poky</title>
+<title>Using the Yocto Project</title>
 
     <para>
         This section gives an overview of the components that make up the Yocto Project