Haiku nightlies site moved!

It was agreed that the nightly downloads location should be a bit more centralized around the main website domain. Oliver and Niels got busy setting up a new buildbot instance and the new nightly pages, and finished it sometime last week.

The "automatic update" repositories have also moved, they can now be (temporarily) found at https://download.haiku-os.org/haiku-repositories/. Sometime before the next release, these will likely be migrated to https://packages.haiku-os.org/, but this is lower priority for now.