Add prolog message about documentation with link to the products pages
Use bold markup for prolog message
Set stable version to 4.4 for the moment
First draft of whats-new.txt block
Suggestions from @melissalinkert
Merge pull request #568 from joshmoore/5-doc-fixes

5.x documentation modifications
Merge pull request #567 from sbesson/transition_docs_message

Add prolog message about documentation with link to the products pages
Add URLs to the What's new page

- Add link for the Imspector format
- Add link to the OME model documentation
specification: Use correct unit and matrix symbols
Use local rather than external links as per Melissa's suggestion
Merge pull request #570 from sbesson/whatsnew_urls

Add URLs to the What's new page
Merge pull request #571 from rleigh-dundee/schema-units

specification: Use correct unit and matrix symbols
Fixing small typos in schema docs
Adding web-extra folder copy to script

The content of any "web-extra" folder will be applied by an
rsync to the publish folder after it is build. I needed this
to test pre-release versions of the schema as they need added
to the website but not included in the generated indexes.
Updating docs link