Specialize the IFileTransferEvent into more pertinent events
Detail this event into sub-types:
* IOutgoingFileTransferEvent - super interface for outgoing file transfer events
* IIncomingFileTransferEvent - super interface for incoming file transfer events
* IFileTransferRequestEvent - represents remote file transfer incoming requests delivered to IIncomingFileTransferRequestListener
Each sub-type will specialize in more detailed events to represent corresponding file transfer occurrences. Ideas:
* IIncomingFileTransferReceiveDataEvent
* IIncomingFileTransferReceiveDoneEvent
* IIncomingFileTransferReceivePausedEvent
* IIncomingFileTransferReceiveResumedEvent
* IIncomingFileTransferReceiveStartEvent
* IOutgoingFileTransferResponseEvent
* IOutgoingFileTransferSendDataEvent
* IOutgoingFileTransferSendDoneEvent
* IOutgoingFileTransferSendPausedEvent
* IOutgoingFileTransferSendResumeEvent