AccountsService: Add PrefersAccentColor to users (#190)

Author: cassidyjames

accountsservice/io.elementary.pantheon.AccountsService.xml

@@ -16,6 +16,30 @@
       <annotation name="org.freedesktop.Accounts.DefaultValue.String" value="24h"/>
     </property>
 
+    <!--
+      PrefersAccentColor:
+
+      What accent color the user prefers for the UI.
+
+      Valid preferences: 
+        0 = No Preference (currently assumes Blue)
+        1 = Red
+        2 = Orange
+        3 = Yellow
+        4 = Green
+        5 = Mint
+        6 = Blue
+        7 = Purple
+        8 = Pink
+        9 = Brown
+        10 = Gray
+
+      Unrecognized preferences should be considered equal to No Preference.
+    -->
+    <property name="PrefersAccentColor" type="i" access="readwrite">
+      <annotation name="org.freedesktop.Accounts.DefaultValue" value="0"/>
+    </property>
+
     <!--
       PrefersColorScheme: