Add support for backlight sensor.

Author: mtwebster

data/org.cinnamon.settings-daemon.plugins.power.gschema.xml.in.in

@@ -1,5 +1,10 @@
 <schemalist>
   <schema gettext-domain="@GETTEXT_PACKAGE@" id="org.cinnamon.settings-daemon.plugins.power" path="/org/cinnamon/settings-daemon/plugins/power/">
+    <key name="ambient-enabled" type="b">
+      <default>true</default>
+      <summary>Enable the ambient light sensor</summary>
+      <description>If the ambient light sensor functionality is enabled.</description>
+    </key>
     <key name="idle-brightness" type="i">
       <default>30</default>
       <summary>The brightness of the screen when idle</summary>