Enhanced `<rbs-document-list/>` to accept a dynamic value

Please note that the dynamic value must define the entire value of the attribute: embedding Angular bindings in a string will lead to unwanted requests to the server.
* This works: `<rbs-document-list collection-url="(= myCollectionUrl =)".../>`
* This does NOT work: `<rbs-document-list collection-url="http://server/rest/query/(= myParam =)".../>`