Rename poky-image.bbclass to core-image.bbclass

(From yocto-docs rev: c4d0d454e5b484246a9a1b0d29da41a85a8f442c)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/poky-ref-manual/extendpoky.xml

@@ -271,7 +271,7 @@ fi
             <programlisting>
 IMAGE_INSTALL = "task-core-x11-base package1 package2"
 
-inherit poky-image
+inherit core-image
             </programlisting>
             <para>
                 By creating a custom image, a developer has total control
@@ -355,7 +355,7 @@ RRECOMMENDS_task-custom-tools = "\
                 <glossterm><link linkend='var-IMAGE_FEATURES'>IMAGE_FEATURES</link></glossterm>
                 variable. 
                 To create these features, the best reference is 
-                <filename>meta/classes/poky-image.bbclass</filename>, which shows how poky achieves this. 
+                <filename>meta/classes/core-image.bbclass</filename>, which shows how poky achieves this. 
                 In summary, the file looks at the contents of the 
                 <glossterm><link linkend='var-IMAGE_FEATURES'>IMAGE_FEATURES</link></glossterm>
                 variable and then maps that into a set of tasks or packages.