Allow voicemail notification dismissal to be configurable.

If a device/carrier allows it, a voicemail notification in the
notification bar should be dismissable. Note that this change does not
wipe the notification completely, i.e. it will come back if the user
restarts the phone.
Add configuration values relevant to Verizon for non-dismissable
notifications.

Bug: 7888110
Change-Id: I7af4a610fb2ba330633157abcc59f8940372fd85
diff --git a/res/values/config.xml b/res/values/config.xml
index 881762d..b7e3208 100755
--- a/res/values/config.xml
+++ b/res/values/config.xml
@@ -152,4 +152,8 @@
 
     <!-- After a CDMA conference call is merged, the swap button should be displayed. -->
     <bool name="support_swap_after_merge" translatable="false">true</bool>
+
+    <!-- Determine whether the voicemail notification is persistent in the notification bar.
+         If true, the voicemail notifications cannot be dismissed from the notification bar. -->
+    <bool name="voicemail_notification_persistent">false</bool>
 </resources>