Cannot modify or copy document types who are classifiable (patch attached)

Step to reproduce: in the latest Go-Green, go to configuration editor and try to copy the type FAQ which is defined as follow in the CND:

[hippogogreen:faq] > hippogogreen:basedocument, hippostd:relaxed, hippotaxonomy:classifiable

Result: it fails with stacktrace:

[INFO] [talledLocalContainer] 03.09.2013 14:23:19 INFO [org.onehippo.cms7.autoexport.Extension.export():74] Exporting hippoecm-extension.xml in module content
[INFO] [talledLocalContainer] 03.09.2013 14:23:24 ERROR [org.apache.wicket.DefaultExceptionMapper.internalMap():123] Unexpected error occurred
[INFO] [talledLocalContainer] java.lang.IllegalStateException: node with path /hippo:namespaces/hippogogreen/faqtwo/hipposysedit:prototypes/hipposysedit:prototype is not classi
fiable
[INFO] [talledLocalContainer] at org.onehippo.taxonomy.plugin.MixinClassificationDaoPlugin.getClassification(MixinClassificationDaoPlugin.java:69)
[INFO] [talledLocalContainer] at org.onehippo.taxonomy.plugin.TaxonomyPickerPlugin$3.load(TaxonomyPickerPlugin.java:219)
[INFO] [talledLocalContainer] at org.onehippo.taxonomy.plugin.TaxonomyPickerPlugin$3.load(TaxonomyPickerPlugin.java:213)

The copy indeed doesn't have all the mixins.