Add webdav support to all the portlets using DDM in a consistent way

Currently this behaves showing all DDMStructures & DDMTemplates in the same webdav folder, but should be separated per portlet.
The available folders should be:
document_library -> documents
journal -> structures & templates
dynamic_data_lists -> structures & templates
application_display_templates -> templates

Different portlets should have different webdav urls:
we can differentiate using classNameId of the entity, so that webdav urls look like this:

http://localhost:8080/webdav/guest/11223/ddmStructures/10703 (for journal ddm structures)
or
http://localhost:8080/webdav/guest/11754/ddmStructures/10703 (for dynamic data lists ddm structures)