Add a thread to build xml_queryresult table when metacat startup
xml_queryresult table is a big addition to improve metacat query performance. Currently metacat will build records of xml_queryresult when a query first hit it. If we build them during the metacat startup, everytime metacat can get results from xml_queryresult rather than from xml_node table.
The returnfield sets will be the returnfields in metacat common query clients, e.g., morpho, kepler and all skins.