Add gtk3 support
Add gtk3 support

Siedlerchr/jabref,zellerdev/jabref,sauliusg/jabref,sauliusg/jabref,sauliusg/jabref,Siedlerchr/jabref,zellerdev/jabref,zellerdev/jabref,JabRef/jabref,zellerdev/jabref,Siedlerchr/jabref,JabRef/jabref,zellerdev/jabref,JabRef/jabref,JabRef/jabref,Siedlerchr/jabref,sauliusg/jabref