core: Make plugin loader watch on config
core: Make plugin loader watch on config

Now it is possible to enable/disable plugins on the fly by changing the
configuration files.

Signed-off-by: Jens Georg <1d6e1cf70ec6f9ab28d3ea4b27a49a77654d370e@jensge.org>

GNOME/rygel,GNOME/rygel,GNOME/rygel