Solr4 compatibility

I included Solr 4.1's jar/wars, with reasonable configuration.  The tests all pass.  The biggest difference is that the default core is no longer at /solr, but rather at /solr/default.  Solr 4+ is multicore by default, so we have to pick a core name.  Other changes include an upgrade from Jetty6 to Jetty8 (per solr's defaults).