Started working on the IMAP add-on itself.

* Renamed imap_config.cpp to ConfigView.cpp, IMAPFolderConfig.(h|cpp)
  to FolderConfigWindow.(h|cpp).
* Got the latter to build.
* Added Settings class to simplify and unify the BMessage based
  settings access.
* Removed the InboundProtocol[Thread] implementation from the build for now.

headers/private/mail/ServerConnection.h

@@ -1,48 +0,0 @@
-/*
- * Copyright 2010-2011, Haiku Inc. All Rights Reserved.
- * Copyright 2010 Clemens Zeidler. All rights reserved.
- *
- * Distributed under the terms of the MIT License.
- */
-#ifndef SERVER_CONNECTION_H
-#define SERVER_CONNECTION_H
-
-
-#include "SupportDefs.h"
-
-
-namespace BPrivate {
-
-
-class AbstractConnection;
-
-
-class ServerConnection {
-public:
-								ServerConnection();
-								~ServerConnection();
-
-			status_t			ConnectSSL(const char* server,
-									uint32 port = 993);
-
-			status_t			ConnectSocket(const char* server,
-									uint32 port = 143);
-			status_t			Disconnect();
-
-			status_t			WaitForData(bigtime_t timeout);
-
-			ssize_t				Read(char* buffer, uint32 length);
-			ssize_t				Write(const char* buffer, uint32 length);
-
-private:
-			AbstractConnection*	fConnection;
-};
-
-
-}	// namespace BPrivate
-
-
-using BPrivate::ServerConnection;
-
-
-#endif // SERVER_CONNECTION_H