SOLR-5950: Maven config: make the org.slf4j:slf4j-api dependency transitive (i.e., not optional) in all modules in which it's a dependency, including solrj, except for the WAR, where it will remain optional. (merged branch_4x r1584474)

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/lucene_solr_4_7@1584480 13f79535-47bb-0310-9956-ffa450edef68