Move message classes to ferretirc.net.messages

src/main/kotlin/com/shr4pnel/ferretirc/net/messages/ServerMessage.kt

@@ -0,0 +1,7 @@
+package com.shr4pnel.ferretirc.net.messages
+
+sealed class ServerMessage {
+    class Cap() : ServerMessage()
+    class Pong(val token: String? = null) : ServerMessage()
+    class UNIMPLEMENTED(val msg: String) : ServerMessage()
+}