-Modified org/alfresco/repository/doclink/doclink.post in order to add support for create links for multiple files too.
-Added a new marker aspect for nodes that have links created: app:linked. This aspect is added when first link is created for file and removed when last link is deleted.
-Added unit test for api: test de api/node/doclink
-Added activity entry for each link creation
-Modified name of the created link in: "Link to <document_name>.url"