packet extension for request.

.../fu_berlin/inf/dpp/test/RequestExtensionProviderTest.java

...rc/de/fu_berlin/inf/dpp/test/net/XMPPTransmitterTest.java

.../fu_berlin/inf/dpp/test/net/mock/StubXMPPTransmitter.java

...in.inf.dpp/src/de/fu_berlin/inf/dpp/net/IChatManager.java

...in.inf.dpp/src/de/fu_berlin/inf/dpp/net/ITransmitter.java

.../fu_berlin/inf/dpp/net/internal/MultiUserChatManager.java

...c/de/fu_berlin/inf/dpp/net/internal/PacketExtensions.java

...de/fu_berlin/inf/dpp/net/internal/PrivateChatManager.java

...berlin/inf/dpp/net/internal/RequestExtensionProvider.java

...u_berlin/inf/dpp/net/internal/RequestPacketExtension.java

...e/fu_berlin/inf/dpp/net/internal/XMPPChatTransmitter.java