Add references to new plugin to core README.md
Add references to new plugin to core README.md

make-all/source-integration,dregad/source-integration,mantisbt-plugins/source-integration,make-all/source-integration,dregad/source-integration,mantisbt-plugins/source-integration,mantisbt-plugins/source-integration,dregad/source-integration,make-all/source-integration