Updated NinjaBlockEthernet Library

I have included the changes I made to the NinjaBlockEthernet library that enable the keep alive Tick and support serialised JSON (needed to parse the Light protocol for example).  Because serialised JSON results in long strings I had to increase the DATA_SIZE and DATA_LEN constants. 

Known issue: Reading from the DATAString on a Tick will fail. You MUST check NinjaBlock.IsTick before trying to read data.

I don't use the NinjaBlockSerial library so it hasn't been updated.