Reduce HexDump logging

[katrash]

Add a flag to LoggingHandler class to disable complete logging of sent/received data dump (the call to ByteBufferUtil.AppendPrettyHexDump) inside FormatByteBufferandFormatByteBufferHolder` as there could be a need to log all the channel events except the hex dump in order to reduce the log size and for security reasons as well.