IMS: add the api to get IMS registration information.

Conflicts:
	src/java/com/android/internal/telephony/Phone.java
	src/java/com/android/internal/telephony/PhoneProxy.java
	src/java/com/android/internal/telephony/imsphone/ImsPhone.java
	src/java/com/android/internal/telephony/imsphone/ImsPhoneCallTracker.java

Bug: 18668325
Change-Id: Id5b0ed420990bde44b3525c7ec22eb37827d649c

Conflicts:
	src/java/com/android/internal/telephony/Phone.java
	src/java/com/android/internal/telephony/imsphone/ImsPhoneCallTracker.java