mediascanner: handle DATE tag

Allow passing DATE tag to MediaScanner in order to use it to retrieve the year, if YEAR tag isn't
present (see http://review.cyanogenmod.org/#/c/101467

)

Change-Id: I928177e5473262a45b1041a58f381a00d67e2995
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>