Allow Lucene's query parser to be configured

Support configuration of Lucene query parser in collection.xconf:

<parser class="org.apache.lucene.queryparser.analyzing.AnalyzingQueryParser"/>

Parser class should either be a subclass of org.apache.lucene.queryparser.classic.QueryParserBase or org.exist.indexing.lucene.QueryParserWrapper (of which StandardQueryParser is the only implementation right now).