Adds an optional interface to BrowseNode that can be used to query whether a node can be copied and also invoke the actual copy. The goal is to use this from the macro dialogs in later patches to support drag and drop of script files. Change-Id: I396a493d704d481b8f0d52c16a77f6452159d76e Reviewed-on: https://gerrit.libreoffice.org/c/core/+/207736 Tested-by: Jenkins Reviewed-by: Neil Roberts <nroberts@libreoffice.org>