Made the Identify button square

It had been stretched vertically due to the two text labels stretching
the whole grid.  Now the button is square, because it's set to align
center rather than fill.

data/select-list-row.ui

         <property name="top_attach">0</property>
       </packing>
     </child>
+    <child>
+      <object class="GtkButton" id="identify">
+        <property name="visible">True</property>
+        <property name="can_focus">True</property>
+        <property name="receives_default">True</property>
+        <property name="tooltip_text" translatable="yes">Identify device</property>
+        <property name="halign">center</property>
+        <property name="valign">center</property>
+        <property name="image">identify-image</property>
+        <signal name="clicked" handler="on_identify_clicked" swapped="no"/>
+      </object>
+      <packing>
+        <property name="left_attach">1</property>
+        <property name="top_attach">0</property>
+        <property name="height">2</property>
+      </packing>
+    </child>
     <child>
       <object class="GtkLabel" id="device">
         <property name="visible">True</property>
         <property name="top_attach">1</property>
       </packing>
     </child>
-    <child>
-      <object class="GtkButton" id="identify">
-        <property name="visible">True</property>
-        <property name="can_focus">True</property>
-        <property name="receives_default">True</property>
-        <property name="tooltip_text" translatable="yes">Identify device</property>
-        <property name="image">identify-image</property>
-        <signal name="clicked" handler="on_identify_clicked" swapped="no"/>
-      </object>
-      <packing>
-        <property name="left_attach">1</property>
-        <property name="top_attach">0</property>
-        <property name="height">2</property>
-      </packing>
-    </child>
   </object>
 </interface>