Change Resources page to Training Course Material page

This replaces the Resources page with one detailing available material for use in Training courses. Most of the links on the page remain the same, but the link to the downloads folder is new and the CLS Public Demo link is updated.

Appropriate resources have been uploaded to the staging.downloads.openmicroscopy.org site.

Check text reads OK and CLS Public Demo link works. a5-brochure link will not work until active downloads site is updated.