Enable turn on/off Favorites/Loved feature. (#917)

* Added option to enable/disable favorites in Song

* Added option to enable/disable favorites in Artist

* Added option to enable/disable favorites in Albums and Favorites tab in sidebar

* Added option to enable/disable favorites in Player

* Set default value of enableFavourites as true

* Improved the functionality to enable/disable Favorites

* Add `EnableFavourites` config option

Co-authored-by: Deluan <deluan@navidrome.org>

conf/configuration.go

@@ -40,6 +40,7 @@ type configOptions struct {
 	CoverJpegQuality       int
 	UIWelcomeMessage       string
 	EnableGravatar         bool
+	EnableFavourites       bool
 	GATrackingID           string
 	AuthRequestLimit       int
 	AuthWindowLength       time.Duration
@@ -143,6 +144,7 @@ func init() {
 	viper.SetDefault("coverjpegquality", 75)
 	viper.SetDefault("uiwelcomemessage", "")
 	viper.SetDefault("enablegravatar", false)
+	viper.SetDefault("enablefavourites", true)
 	viper.SetDefault("gatrackingid", "")
 	viper.SetDefault("authrequestlimit", 5)
 	viper.SetDefault("authwindowlength", 20*time.Second)