Renamed to "Page models"

I think this is a good place to add some general usage docs so made the name more generic.

docs/index.rst

@@ -14,7 +14,7 @@ Below are some useful links to help you get started with Wagtail.
 
 * **Creating your Wagtail site**
 
-  * :doc:`topics/creating_pages`
+  * :doc:`topics/pages`
   * :doc:`topics/writing_templates`
   * :doc:`topics/images/index`
   * :doc:`topics/search/index`

docs/topics/index.rst

@@ -5,7 +5,7 @@ Topics
 .. toctree::
     :maxdepth: 2
 
-    creating_pages
+    pages
     writing_templates
     images/index
     search/index

docs/topics/pages.rst

@@ -1,6 +1,6 @@
-====================
-Creating page models
-====================
+===========
+Page models
+===========
 
 Each page type (a.k.a Content type) in Wagtail is represented by a Django model. All page models must inherit from the :class:`wagtail.wagtailcore.models.Page` class.