Added css class div.warning, used for the known issue docs quickfix on M1.
Added release-notes directory and notes for 0.5.0-M2.
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.
Adds link to release-notes (in download.html)
Release notes list formatting fix.