Improve Bio-Formats downloads page

Fix https://trac.openmicroscopy.org.uk/ome/ticket/11651

This PR redesigns the Bio-Formats downloads page using the same template as the one used for the OMERO download pages. Additionally the Bio-Formats page is divided into four sections (Tools, Components, Code and Legacy).

The descriptions have been copied over from the previous downloads page but some of them may be redundant with the explicit icons.

/cc @melissalinkert, @gusferguson, @hflynn