Finalise plugin namespace

We've changed method org.hippoecm.frontend.editor.builder.TemplateBuilder#processFieldAdded to respect the new isPlugin attribute of a nodetype. We get the template of the type and we copy over all the properties.

Clean up the taxonomyField root node (/hippo:namespaces/system/taxonomyField/editor:templates/_default_/root
) to only contain the properties that make sense to copy. Also clean up code that copies the properties