anitagraser.com/2017/08/29/fixing-invalid-polygon-geometries/
wfs-t
Icon-Probleme in Plugins
gis.stackexchange.com/questions/162707/when-i-change-a-qgis-plugins-icon-why-doesnt-it-change-in-the-menu-toolbar
stackoverflow.com/questions/9324670/qgis-python-icon-in-label
gis.stackexchange.com/questions/115834/no-plugin-icon-in-the-toolbox-in-qgis-2-4
www.qgistutorials.com/en/docs/building_a_python_plugin.html
gis.stackexchange.com/questions/144593/create-a-checkbox-per-loaded-layer-in-a-qgis-plugin
smime.p7s