gplugin/gplugin

Merged in feature/plugin-errors (pull request #77)
develop
2020-05-21, Gary Kramlich
f7de83d8ea56
Merged in feature/plugin-errors (pull request #77)

Add an error property to GPluginPlugin and fix the ui/tests/etc that were affected by it.

Approved-by: Elliott Sales de Andrade
The following individuals have contributed to this project.
Ankit Vani <a@nevitus.org>
EionRobb <eion@robbmob.com>
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>
Olaf Hering <olaf@aepfle.de>
Richard Laager <rlaager@pidgin.im>