lua-factory: Block plain text queries when source doesn't advertise it
lua-factory: Block plain text queries when source doesn't advertise it

To avoid sources from doing plain text queries without advertising them,
verify the schemes used by the URLs passed to grl.fetch.

https://bugzilla.gnome.org/show_bug.cgi?id=747953

GNOME/grilo-plugins,GNOME/grilo-plugins,jasuarez/grilo-plugins,grilofw/grilo-plugins,jasuarez/grilo-plugins,MikePetullo/grilo-plugins,grilofw/grilo-plugins,MikePetullo/grilo-plugins,MikePetullo/grilo-plugins