Moving KPlugionLoader|Factory to KCoreAddons?

[Alex Merry]

While doing work on KService, I realised that KPluginLoader,
KPluginFactory and KExportPlugin could all quite happily go in
KCoreAddons, and it would be really nice to have them there
(KPluginTrader would stay in KService, of course).

I'm not sure of the BCness or SCness of this, though.  I think it might
be BC, since KService links to KCoreAddons.  We'd have to include
KCoreAddons in KService's link interface, since kservice.h uses
KPluginLoader and KPluginFactory in a template method, so I think it
would also be SC.

If that's the case (the SCness in particular), does that move seem
reasonable?

Alex