Create a full page text, rather than a button, in notebook sample

This is much more realistic and looks less weirdly.

Also add the text directly as a page, without wrapping it in a panel,
just to show that this is possible and works too.

No real changes.

samples/notebook/notebook.h

@@ -189,7 +189,7 @@ enum ID_COMMANDS
 #define I_WAS_INSERTED_PAGE_NAME        "Inserted"
 #define RADIOBUTTONS_PAGE_NAME          "Radiobuttons"
 #define VETO_PAGE_NAME                  "Veto"
-#define MAXIMIZED_BUTTON_PAGE_NAME      "Maximized button"
+#define TEXT_PAGE_NAME                  "Text"
 
 // Pages that can be added by the user
 #define INSERTED_PAGE_NAME              "Inserted "