Show sync-off alert

In all contacts list:
alert user when global sync is off if user never dismissed before,
until sync setting is toggled on then off again.

In account view:
when global sync is off, show alert with the same logic for all
contacts list;
when global sync is on, alert user when contacts sync for this account
is off if user never dismissed before, until contacts sync is toggled
on then off again.

Bug: 31755559

Test: Manually tested the scenarios:
1) Add/remove account,
2) switch between all contacts list, account view, and label views,
3) update contacts information,
3) turn on sync/dismiss from alert,
when global sync is on/off, contacts syncs are all on/off, contacts
sync is on/off for a particular account.

Change-Id: Id5001847270d5a984942c63a42edb5f9401bc2c2
diff --git a/res/values/colors.xml b/res/values/colors.xml
index 98c522d..e2024fd 100644
--- a/res/values/colors.xml
+++ b/res/values/colors.xml
@@ -260,4 +260,7 @@
 
     <!-- tint color for device account icons -->
     <color name="device_account_tint_color">#7f7f7f</color>
+
+    <!-- Background color for sync-off alert. -->
+    <color name="alert_background">#e0e0e0</color>
 </resources>