Added rsyslog rule to filter out swift-proxy messages into separare log file

See https://bugzilla.novell.com/show_bug.cgi?id=879931

Some notes:
 - we have defined 30-swift.conf.erb that should be deployed by slog recipe
 - I have a feeling that slog part is obsolete/not working anyway
 - if that is true, I'd propose to also remove slog related parts
 - BTW, using that 30-swift.conf.erb instead of new 11-swift-proxy.conf.erb does not seem to work

Creation of the log directory would be done in package spec file.