Merge back several "low hanging" bug fixes into the 4.8 branch...
SOLR-6029: r1590867
SOLR-6030: r1591555
SOLR-6037: r1591800
SOLR-6023: r1592195
SOLR-5090: r1592591
SOLR-6039: r1592605
SOLR-5993: r1588415
SOLR-5904: r1587702



git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/lucene_solr_4_8@1592821 13f79535-47bb-0310-9956-ffa450edef68