core: Create predefined relations with key "url"
core: Create predefined relations with key "url"

System-defined keys "url", "mime-type", "bitrate", "framerate", "height" and
"width" are correlated.

Signed-off-by: Juan A. Suarez Romero <af79b5692270b306571bb1d8bbe0285ae3ac93d9@igalia.com>

kyoushuu/grilo,MathieuDuponchelle/grilo,kyoushuu/grilo,grilofw/grilo,jasuarez/grilo,jasuarez/grilo,GNOME/grilo,MathieuDuponchelle/grilo,GNOME/grilo,grilofw/grilo,grilofw/grilo,MathieuDuponchelle/grilo,jasuarez/grilo,kyoushuu/grilo,kyoushuu/grilo