- Make compilation to GTK3 optional.

- Use GDbus for communication.
- Add execute menu item to launch without closing the window.
- Add default action to open absolute paths.
- Add bookmarks in the model.
- Do nothing with the Tab event during competion (bug #10187).
- Use new xdg function to set environment.
- Translation updates: Amharic, Arabic, Belarusian, Bulgarian,
  Bengali (India), Catalan (Valencian), Czech, Danish, German,
  Dzongkha, Greek, English (Australia), English (United Kingdom),
  Spanish (Castilian), Estonian, Basque, Persian, Finnish, French,
  Galician, Gujarati, Croatian, Hungarian, Armenian, Indonesian,
  Icelandic, Italian, Japanese, Georgian, Kazakh, Korean, Kurdish,
  Lithuanian, Macedonian, Marathi, Malay, Dutch (Flemish), Norwegian
  Nynorsk, Occitan (post 1500), Polish, Portuguese, Portuguese
  (Brazilian), Romanian, Russian, Slovak, Slovenian, Serbian, Swedish,
  Thai, Turkish, Uyghur, Ukrainian, Chinese (China), Chinese (Hong
  Kong), Chinese (Taiwan).