Update catalog.xml to point at maven-central

- Instead of pointing at oss.sonatype.org, point at maven.org for
  brooklyn M2 artifacts
Fix docs build: re-add eclipse.include.md

- docs/use/guide/quicksart/eclipse.include.md had been accidentally
  deleted, which caused the jekyll build to fail. This commit
  reinstates that file.
Merge pull request #578 from jdtoy/master

Release notes for M2 branch.
Adds link to release-notes (in download.html)
Release notes list formatting fix.