#4 SimiDic Builder should convert HTML entities to text for the definition previews in search mode

[amosbatto]

In the Pango markup language (which StarDict uses), all <, > and " should be converted to their HTML entities: &lt; &gt; &quote;

The code of SimiDic Builder needs to be changed so it correctly converts all HTML entities to text so they can be displayed correctly in the previews of definitions in the search mode.
Specifically:
&lt; --> <
&gt; --> >
&quote; --> "