hook up replaygain config file options

backend/config.go

@@ -58,6 +58,12 @@ type ScrobbleConfig struct {
 	ThresholdPercent     int
 }
 
+type ReplayGainConfig struct {
+	Mode            string
+	PreampGainDB    float64
+	PreventClipping bool
+}
+
 type Config struct {
 	Application    AppConfig
 	Servers        []*ServerConfig
@@ -69,6 +75,7 @@ type Config struct {
 	PlaylistPage   PlaylistPageConfig
 	LocalPlayback  LocalPlaybackConfig
 	Scrobbling     ScrobbleConfig
+	ReplayGain     ReplayGainConfig
 }
 
 func DefaultConfig() *Config {
@@ -106,6 +113,11 @@ func DefaultConfig() *Config {
 			ThresholdTimeSeconds: 240,
 			ThresholdPercent:     50,
 		},
+		ReplayGain: ReplayGainConfig{
+			Mode:            ReplayGainNone,
+			PreampGainDB:    0.0,
+			PreventClipping: true,
+		},
 	}
 }