Configurable Resend packet delay for reliable packets

[sebas77]

Hi, this is an idea more than an issue. We decided to add these parameters

    /// <summary>
        /// Custom development: Fixed part of the NetPeer resend delay
        /// </summary>
        public double ResendFixedDelay = 25.0;

        /// <summary>
        /// Custom development: Multiplication factor of Rtt in the NetPeer resend delay calculation
        /// </summary>
        public double ResendRttMultiplier = 2.1;

to tune the delay time to re-send a packet waiting for a hack. Some time we just want to be more aggressive at the cost of more bandwidth. Thoughts?