all: Bump API and ABI version

Signed-off-by: Jens Georg <mail@jensge.org>
server: Move date and creator to MediaObject

Split out of the patch from 720218

Signed-off-by: Jens Georg <mail@jensge.org>
server: Move properties up the hierarchy

Move artist, genre and album to MediaObject/AudioItem to make them available in
containers and videos as well

https://bugzilla.gnome.org/show_bug.cgi?id=709723
server: Prevent potential null dereference

Ported from patch in 720223

Signed-off-by: Jens Georg <mail@jensge.org>
test: Remove deprecated functions

Signed-off-by: Jens Georg <mail@jensge.org>