software/wordpress: introduce buildout.hash.cfg

software/wordpress/buildout.hash.cfg

+[application-template]
+_update_hash_filename_ = wp-config.php.in
+md5sum = 0d62b28125ca3c780db0b547199953f2

software/wordpress/software.cfg

 [buildout]
 extends =
   ../../stack/lamp/buildout.cfg
+  ./buildout.hash.cfg
 
 [application]
 url = http://wordpress.org/wordpress-3.5.1.tar.gz
@@ -8,8 +9,7 @@ md5sum = 409889c98b13cbdbb9fd121df859ae3e
 
 [application-template]
 recipe = slapos.recipe.build:download
-url = ${:_profile_base_location_}/wp-config.php.in
-md5sum = 0d62b28125ca3c780db0b547199953f2
+url = ${:_profile_base_location_}/${:_update_hash_filename_}
 download-only = True
 filename = template.in
 mode = 0644