Gh pages reorganisation

[jburel]

For background #398
This PR:

• re-organises the files and move them under docs so we can publish without cluttering the master branch
• adds the redirect plugin
• redirects figure.o.org to https://www.openmicroscopy.org/omero/figure/
• blog posts have been either redirected to the announcements on www.o.org or to the GH file in its final location i.e. master/docs
• removes demo code as agreed with @will-moore
• redirects figure.o.org/demo. This link will need to be updated when the system in Dundee is back.

To test locally go in the docs folder and run docker run -it --rm -p 4000:4000 -v $PWD:/srv/jekyll jekyll/builder:pages jekyll server -w

docs/_site will be added to .gitignore when migrated to master to avoid conflict

[sbesson]

The changes proposed her make sense to me and belong to three categories:

• file removal incl. .gitignore and the content of demo/
• file renaming and addition of redirect_to markup for the html files
• file renaming without modification for the remaining files

Most of the proposed redirects looked legit to me although I'll leave @will-moore to sign-off on these changes.

[will-moore]

Testing locally:

• http://localhost:4000/ redirects to https://www.openmicroscopy.org/omero/figure/
• Same for http://localhost:4000/blog/
• http://localhost:4000/demo/#file/1 redirects to https://omero.lifesci.dundee.ac.uk/figure/file/377002/
• http://localhost:4000/2017/04/19/release-3.0.0.html redirects to https://www.openmicroscopy.org/2017/04/19/figure-3-0-0.html
• http://localhost:4000/2015/04/30/quality-figures-from-omero-figure.html - redirects to https://github.com/ome/omero-figure/blob/master/docs/_posts/2015-04-30-quality-figures-from-omero-figure.markdown (404)

[jburel]

404 is expected until some of the md files are in master

[will-moore]

Good to merge 👍