Document notification retrying

[Franzaine]

When a peripheral is notifying the client that the APDU responses are ready it needs to retry the notification until it is received. Certain phones seem to miss the notification and then the transaction fails. A sensible retry mechanism seems to be retry every second in total 5 times.

[martinpaljak]

Things to consider:

• use indications (with ACK) rather than notifications (no ACK) for increased reliability
• define a recommended retry mechanism for a BLE server implementation, until the response is read (fully)