EBookClient: be more introspectable
EBookClient: be more introspectable

This is mostly a matter of clarifying whose responsibility it is to
free things, in a machine-readable way.

Bug: https://bugzilla.gnome.org/show_bug.cgi?id=695151
Signed-off-by: Simon McVittie <2b470b34502dbf3ba4bcc04ea7e64f4e0e104f33@collabora.co.uk>
Reviewed-by: Matthew Barnes <16b074f26e84167d7f55d437bd68af737de5b166@redhat.com>

Distrotech/evolution-data-server,Distrotech/evolution-data-server,matzipan/evolution-data-server,tintou/evolution-data-server,matzipan/evolution-data-server,tintou/evolution-data-server,matzipan/evolution-data-server,Distrotech/evolution-data-server,tintou/evolution-data-server,matzipan/evolution-data-server,tintou/evolution-data-server,Distrotech/evolution-data-server,Distrotech/evolution-data-server,matzipan/evolution-data-server