Increasing Ringtone

Implemented Increasing Ringtone, when activated the ringing will
if user does not answer start to increase the volume of the ring
signal.

The initial delay before starting to increase the volume is 8s,
then the signal is ramped every 4s up to the max volume of the
ring signal.

Change-Id: I053031ef9d611fcc52c655126c9b51a12160093a