fix is_externally_managed criteria

• exclude externally managed link categories in the sidebar if it is configured
fix wrong behaviour after deleting sidebar item

the content list has to be reloaded when a active sidebar item is deleted
otherwise no entries are displayed and no sidebar item is active
fix initial selection
fix criteria for document list

also documents with no document_category_id should be displayed
fix reloading of list after deleting sidebar item

if a active document category is deleted, the whole list of documents has to be displayed (or alternatively the __without)