Add encryption to binlogrouter

Add encryption of binlog events to the binlogrouter. A similar approach can be taken that was used with MaxScale 2.4 where the following steps were taken to encrypt an event:

• Store the real event length in memory
• Move the 4 byte timestamp into the 4 byte event length field
• Encrypt the data, excluding the 4 bytes from the start of the file that contain the timestamp (now stored where the length is stored)
• Move the 4 bytes of encrypted data stored at the event length field into the 4 bytes where the timestamp is stored
• Store the encrypted event length in the 4 byte event length field