Added missing element to plugin configuration.

The element GuiElement was updated to ExtendedGuiElement, I forgot to add the extra type in the plugin declaration.

Fixed Terraform interface when using behemoth terraforming.

Added Riftborn, added Terraformation Modifier support.

Minor fix in Pugins assembly definitions. I was testing the mod with the public xml files edited.. Corrected.

Initial release. Doesn't affect Riftborn terraforming.