Added beta update support.

Started work on further appimage support

settings.go

@@ -93,12 +93,14 @@ func settingsUI(parent *gtk.Window, onExit func()) {
 	paDirsCheck.Connect("toggled", func() {
 		paDirs = paDirsCheck.GetActive()
 	})
+	betaCheck, _ := gtk.CheckButtonNewWithLabel("Update to beta releases")
 	gnrl.Add(wineLbl)
 	gnrl.Add(dlWine)
 	gnrl.Add(pthdCheck)
 	gnrl.Add(wineCheck)
 	gnrl.Add(versCheck)
 	gnrl.Add(paDirsCheck)
+	gnrl.Add(betaCheck)
 	ntbk.AppendPage(gnrl, getLabel("General"))
 	com, _ := gtk.BoxNew(gtk.ORIENTATION_VERTICAL, 5)
 	com.SetMarginStart(10)