Change order of panel plugins "pulseaudio" and "power-manager"

The "power-manager" shows battery percentage. Those numbers are close to
the clock, which needs a close look to distinguish the numbers. Moving the
"power-manager" plugin left of the "pulseaudio" plugin slightly disturbs
the harmony of having all numbers at the right-hand side but separating them
increases readability.

Now "power-manager" becomes "plugin-6" and "pulseaudio" becomes "plugin-7".

config/xfce4/xfconf/xfce-perchannel-xml/xfce4-panel.xml

@@ -56,10 +56,10 @@
     <property name="plugin-5" type="string" value="systray">
       <property name="icon-size" type="int" value="30"/>
     </property>
-    <property name="plugin-6" type="string" value="pulseaudio">
+    <property name="plugin-6" type="string" value="power-manager-plugin"/>
+    <property name="plugin-7" type="string" value="pulseaudio">
       <property name="enable-keyboard-shortcuts" type="bool" value="true"/>
     </property>  
-    <property name="plugin-7" type="string" value="power-manager-plugin"/>
     <property name="plugin-8" type="string" value="separator">
       <property name="style" type="uint" value="0"/>
     </property>