Introduction of the new SAP-UIM socket

Added new socket connection for communication between the SAP module
in Telephony and User Identity Module with DSDA support.

New classes added are:

RilSocket
---------
Base class(virtual) for any type of socket. Has listen
and commands callbacks similar to that of the existing
telephony->rild socket.

RilSapSocket
------------
Derived class for socket for communication between BT SAP
and the sim module in the modem. It initialises
socket, calls Sap_Uim_Init to get the handles and
starts the socket thread.

rilSocketQueue
--------------
Queue for managing socket requests.

Change-Id: I8828173941d6ae76f1f9cc0d567efaf41a77d175