https://github.com/volaya/plugin-writing-course/blob/master/plugins.rst http://blog.habrador.com/2013/02/how-to-generate-random-terrain.html http://www.geoinformations.developpement-durable.gouv.fr/fichier/pdf/FOAD_Fonction_Action_cle7fa658.pdf?arg=177833603&cle=1034f2aebb6d17e1cd1b671336dbb55c7c6c595c&file=pdf%2FFOAD_Fonction_Action_cle7fa658.pdf https://github.com/wonder-sk/qgis-minimal-plugin