Support for sidecar files is a new feature in MC14. A sidecar file is an xml file that contains metadata and is useful when the media format does not support internal tags.
To get metadata from an MC13 library into an MC14 library, you can just import the MC13 library into MC14.
In MC14, sidecar files can be used in the following way:
Tag movies in MC14 on one computer. Choose Library Tools > Update Tags (from library). This will save a sidecar file in the folder of the movie. For DVD in VIDEO_TS folder, the sidecar file is simply named VIDEO_TS_ifo_JRSidecar.xml, inside the VIDEO_TS folder.
On a different computer, you can import the movies into MC14. The tags will be imported.