Solr Query API searches by default only in technical documents

The reason for this is because the xwiki.supportedLocales Solr query parameter defaults to the ROOT locale which means that if you don't specify this parameter then the search will look only for documents without a language (technical documents). This is quite unexpected for someone that tries to use the Solr Query API and forgets to set this parameter. It should default to the configured list of supported locales instead. In other words, you should not have to set it to the list of configured locales, the Solr Query API should do this for you. Of course, we should still be able to overwrite it.