Cert update release v27-12

Our 10 year long certs expired, so new release is needed or windows users can't install the software.

Thanks for user community to tell me about this kind of issues, since its been uninstallable for 2 months now without anyone giving e-mail.

New features:

 1) gltf animations are working better.
 2) gltf animations are being used in meshpage.org/view.php and meshpage.org/gltf_to_zip.php
 3) colours in gltf shader are now brighter
 4) gltf shader now supports light direction vector specification. (required binary compatibility break)
 5) sanmiguel is again working in web
 6) concurrent download file sizes are working again