STANBOL-1139: added a INFO level logging when starting to enhance a ContentItem with a chain. This is printed on the EnhancementJobManager logger introduced by STANBOL-1267

git-svn-id: https://svn.apache.org/repos/asf/stanbol/branches/release-0.12@1565226 13f79535-47bb-0310-9956-ffa450edef68