introduced support for sending and receiving messages

app/src/main/kotlin/com/tutpro/baresip/Message.kt

@@ -0,0 +1,7 @@
+package com.tutpro.baresip
+
+import java.io.Serializable
+
+class Message(val aor: String, val peerURI: String, val direction: Int, val message: String,
+              val timeStamp: Long, var new: Boolean): Serializable {
+}