Add new downloads table for the Bio-Formats C++ artifacts

This should set-up all the infrastructure required for exposing the Bio-Formats C++ artifacts in the 5.1.x series. /cc @rleigh-dundee @melissalinkert

I am currently using the generic OME icon but we may want to have dedicated icons for each binary /cc @gusferguson

--no-rebase
This needs a full stop too so it matches the sentence above.