core: Only emit notifications for multi-valued properties when necessary

core: Only emit notifications for multi-valued properties when necessary

Previously, notifications were emitted whenever a related Persona’s property
changed, even if it had no effect on the Individual’s property. This was
causing infinite loops of notifications-then-getters-being-called in some
of the EDS tests. Bad.

This is fixed by only emitting notifications on Individuals’ multi-valued
properties if the properties have actually changed. Of course, this
requires lots of copying and pasting the same code because Vala doesn’t
have a preprocessor and delegates aren’t up to the job. Sigh.

See: https://bugzilla.gnome.org/show_bug.cgi?id=682809