gplugin/gplugin

we were only using libgladeui to figure out where to install the catalog, but we should only be installing to our prefix, so do that and drop the dep
The following individuals have contributed to this project.
Ankit Vani <a@nevitus.org>
EionRobb
Elliott Sales de Andrade <quantum.analyst@gmail.com>
Gary Kramlich <grim@reaperworld.com>
Jason Scherer <schereja@gmail.com>
John Bailey <rekkanoryo@rekkanoryo.org>
Mike Ruprecht <cmaiku@gmail.com>
Richard Laager <rlaager@pidgin.im>