MSIM support for Statusbar.

-Add support for Signal Strength icon display for MultiSim

Display dual subscription info in notification panel
  -Show subscription information for both subscriptions
   relevant to the sim state. if sim state is ready show
   operator name, if card absent, show no sim message,
   if UE is in airplane mode, show airplane mode message.

Clear data activity icon when disconnected
  -If data is disconnected before data activity becomes none,
   then clear up/down arrow icon by reset the data activity icon.

Add support for ro.config.combined_signal
  -Add support for ro.config.combined_signal. This property is being used
   to consider data service state for signal display.
   When ro.config.combined_signal is not set to false, we will display
   CS/PS signal strength whichever is available

Conflicts:
packages/SystemUI/src/com/android/systemui/statusbar/phone/PhoneStatusBarPolicy.java
packages/SystemUI/src/com/android/systemui/statusbar/policy/NetworkControllerImpl.java
Change-Id: Iebc9f49334a8a3cf469ea2624f0e1d6eb50b63bc