Add method in TelecomManager to return line1Number for a PhoneAccount.

Since we do not want to expose SubIds in the app layer, we need a
wrapper to extra the subId from a PhoneAccount and return the
value of TelephonyManager#line1Number.
Also update error strings to be more consistent.

Bug: 19087382
Change-Id: Ie5a474d45336921d1007b36a4d26cd4da68f8b91
diff --git a/telecomm/java/com/android/internal/telecom/ITelecomService.aidl b/telecomm/java/com/android/internal/telecom/ITelecomService.aidl
index f8d7539..d2030f2 100644
--- a/telecomm/java/com/android/internal/telecom/ITelecomService.aidl
+++ b/telecomm/java/com/android/internal/telecom/ITelecomService.aidl
@@ -126,6 +126,11 @@
     boolean hasVoiceMailNumber(in PhoneAccountHandle accountHandle);
 
     /**
+     * @see TelecomServiceImpl#getLine1Number
+     */
+    String getLine1Number(in PhoneAccountHandle accountHandle);
+
+    /**
      * @see TelecomServiceImpl#getDefaultPhoneApp
      */
     ComponentName getDefaultPhoneApp();