Changes in 3.18.0

* Use "resize" property and fix a bug in panel widget (Vladimir Motilenko)
* bgo #751239: fix preview window color (Lukas K)
* bgo #729325 - Set type hint of dragged-out windows to TOOLBAR (Lukas K)

* Translation: ca Jordi Ma
* Translation: pl Piotr Drąg
* Translation: pt Pedro Albuquerque