Support list with newline.

In case if profile overrides another one and adds new list like:

[local-bt5-repository]
list += something

something will be separated by newline instead of space. Thanks to iterating
over such quoted list it is possible to give maximum flexibility in overriding.

stack/erp5.cfg

@@ -142,7 +142,7 @@ recipe = plone.recipe.command
 stop-on-error = true
 genbt5list = ${erp5:location}/product/ERP5/bin/genbt5list
 command =
-  ${buildout:executable} ${:genbt5list} ${local-bt5-repository:list}
+  for d in "${local-bt5-repository:list}" ; do cd $d && (${buildout:executable} ${:genbt5list} ; cd -) ; done
 update-command = ${:command}
 
 [bootstrap2.6]