fix xmlEncode and concat sed command

[zhaocai]

1. fix ' Otherwise, you get

<?xml version="1.0"?>
<items>
  <item uid="uid'" arg="arg'" valid="valid" autocomplete="autocomplete">
    <title>title'</title>
    <subtitle>subtitle'</subtitle>
    <icon>icon.png'</icon>
  </item>
</items>

extra ' is added to each item

1. should add /g for sed
2. faster to concatenate sed commands