SOLR-6476 refactored to get the Operation class outside

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_5x@1631400 13f79535-47bb-0310-9956-ffa450edef68
SOLR-5852: Add CloudSolrServer helper method to connect to a ZK ensemble

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_5x@1631411 13f79535-47bb-0310-9956-ffa450edef68
SOLR-6476 change the error message

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_5x@1631421 13f79535-47bb-0310-9956-ffa450edef68
SOLR-6485 added javadocs

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_5x@1631429 13f79535-47bb-0310-9956-ffa450edef68