Add support to send dtmf for SCH tone

Add methods to send/stop dtmf as per subscription.

Change-Id: Ia17a733bd6ec1cd0163024d12c021e1e21032078
CRs-Fixed: 610582
MSIM(DSDA): Add conversation sub

Add conversation sub

Change-Id: I67f508baf66ba5ebc86a4f430af739d6ba8180ba
CRs-Fixed: 659123
Merge remote-tracking branch 'cyanogen/cm-11.0' into cm-11.0