Core: Make application title customizable for WL (#22401)

* Core: Add custom app title

* Docs: Update White Labeling title customization

* Core: set back export for Branding types

pkg/api/dtos/index.go

@@ -17,6 +17,7 @@ type IndexViewData struct {
 	AppNameBodyClass        string
 	FavIcon                 string
 	AppleTouchIcon          string
+	AppTitle                string
 }
 
 type PluginCss struct {

pkg/api/index.go

@@ -87,6 +87,7 @@ func (hs *HTTPServer) setIndexViewData(c *m.ReqContext) (*dtos.IndexViewData, er
 		AppNameBodyClass:        getAppNameBodyClass(hs.License.HasValidLicense()),
 		FavIcon:                 "public/img/fav32.png",
 		AppleTouchIcon:          "public/img/apple-touch-icon.png",
+		AppTitle:                "Grafana",
 	}
 
 	if setting.DisableGravatar {