Make doc links incl. minor version in URL

Doc links need to be 5.1 in the downloads pages for the 5.1.0-m1 internal release and 5.0 for the other docs once we release a full 5.1.0 version (as /support/omero5/ and /support/bio-formats5/ will both be redirected to the 5.1 docs once we release publicly). This updates doc links on the OMERO and BF download pages.

To be rebased to dev_5_0 once the 5.0 redirects are in place cc @qidane