- Switched from subsonic-response in xml to response in json

- Retrofitting of all Subsonic models

app/src/main/java/com/cappielloantonio/play/subsonic/base/ApiResponse.kt

@@ -0,0 +1,9 @@
+package com.cappielloantonio.play.subsonic.base
+
+import com.cappielloantonio.play.subsonic.models.SubsonicResponse
+import com.google.gson.annotations.SerializedName
+
+class ApiResponse {
+    @SerializedName("subsonic-response")
+    var subsonicResponse: SubsonicResponse? = null
+}