Do not show property panel by default.

Property panel sometimes hides text entry box on firefox in case
the mode is auto-hide because firefox does not provide the right
cursor locations and firefox does not update cursor locales
when preedit is updated so property panel hides text entry box
for a while and auto-hide is not useful with firefox and thunderbird.

TEST=gsettings reset org.freedesktop.ibus.panel show

Review URL: https://codereview.appspot.com/90480043

data/ibus.schemas.in

@@ -161,7 +161,7 @@
       <applyto>/desktop/ibus/panel/show</applyto>
       <owner>ibus</owner>
       <type>int</type>
-      <default>1</default>
+      <default>0</default>
       <locale name="C">
         <short>Auto hide</short>
 	    <long>The behavior of property panel. 0 = Do not show, 1 = Auto hide, 2 = Always show</long>

ui/gtk3/propertypanel.vala

@@ -34,7 +34,7 @@ public class PropertyPanel : Gtk.Box {
     private IPropToolItem[] m_items;
     private Gdk.Rectangle m_cursor_location = Gdk.Rectangle(){
             x = -1, y = -1, width = 0, height = 0 };
-    private int m_show = PanelShow.AUTO_HIDE;
+    private int m_show = PanelShow.DO_NOT_SHOW;
     private uint m_auto_hide_timeout = 10000;
     private uint m_auto_hide_timeout_id = 0;
     private bool m_follow_input_cursor_when_always_shown = false;