Add support for data+Mms

1. Add makePhoneSwitcher method to create PhoneSwitcher object.
2. Modify visibility of member variables required for this feature.

Change-Id: I0ad5d73573be9485510b9f4be6fa0b9a5d3a5f8d
CRs-Fixed: 1048079

Dual data feature

Add support for Volte+PS feature.
User can have default pdn on one sub and on-demand pdn like ims, mms
on other sub simultaneously.

Change-Id: I8da754ed78c4ec8737a5055af5807915f4e150ac
CRs-Fixed: 1059913