Show the element editor's Informations tab for Terminal and Thumbnail

setTabVisible(1, ...) only allowed Simple and Master, but the tree
(updateTree()) and the actual write path (ElementScene::toXml()) both
already support elementInformations for Terminal and Thumbnail too --
three independent "is this type allowed" checks that were never
reconciled, leaving already-working support unreachable through the
UI for those two types. Slave stays excluded here, consistent with
having no elementInformations support at either of the other two
points either (separate, larger gap, not addressed here).

sources/editor/ui/elementpropertieseditorwidget.cpp

@@ -425,7 +425,9 @@ void ElementPropertiesEditorWidget::on_m_base_type_cb_currentIndexChanged(int in
 
 	ui->tabWidget->setTabVisible(1,
 								 (type_ == ElementData::Simple ||
-								  type_ == ElementData::Master));
+								  type_ == ElementData::Master ||
+								  type_ == ElementData::Terminal ||
+								  type_ == ElementData::Thumbnail));
 
 	updateTree();
 }