SOLR-6058: Include the new Solr logo and favicon in Solritas (/browse UI) as well as in generated per-release Solr documentation; switch all favicon links' Content-Type: 'image/ico'->'image/x-icon' (merged trunk r1646609)

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_5x@1646610 13f79535-47bb-0310-9956-ffa450edef68