Telephony(MSIM): Add prompt support for SMS

1) Add prompt option in SMS multi sim settings.
2) New iterface API to get SMS prompt is enabled or not.
3) Disply prompt while sending SMS, if user selects
   prompt mode in multi sim settings.
CRs-fixed: 474694

Change-Id: Iea9e8a4ea4f413316604a3d66ece624eab75ee26
Telephony: Add support for tune away and priority sub

Add constants for tune away and priority subscription
CRs-fixed: 464483

Change-Id: I790cfdcd9a1dee946502349084a4d8138d2144ec