Fix lucene analyzer configuration

[bugfix] Lucene index configuration: constructor of default analyzers now expect stopword lists to be provided in a CharArraySet instead of a Set, e.g.:

```xml
<analyzer class="org.apache.lucene.analysis.standard.StandardAnalyzer">
    <param name="stopwords" type="org.apache.lucene.analysis.util.CharArraySet"/>
</analyzer>
```