Remove dependence on CareLink to get CNL HMAC and encryption key.

...o/nightscout/android/medtronic/GetHmacAndKeyActivity.java

...info/nightscout/android/medtronic/MedtronicCnlReader.java

...nfo/nightscout/android/medtronic/MedtronicCnlSession.java

...droid/medtronic/message/ContourNextLinkBinaryMessage.java

...ut/android/medtronic/message/MedtronicReceiveMessage.java

...roid/medtronic/message/RequestLinkKeyResponseMessage.java

.../android/medtronic/service/MedtronicCnlIntentService.java

...tscout/android/model/medtronicNg/ContourNextLinkInfo.java