gplugin/gplugin

merge the feature/gtk-doc branch with ALL of the changes
develop
2018-05-07, Gary Kramlich
07ba62616ebf
merge the feature/gtk-doc branch with ALL of the changes
export GPLUGIN_VERSION=@GPLUGIN_MAJOR_VERSION@.@GPLUGIN_MINOR_VERSION@.@GPLUGIN_MICRO_VERSION@