detect the first upload and tweak the RFS template

From https://lists.debian.org/debian-mentors/2020/06/msg00260.html :

Changes since the last upload:

What "last upload"? This is the first release into Debian. And thus, there's no history yet

Indeed, we could probably do better, and change the template to detect if there is only one paragraph in the changelog and if so instead of saying "Changes since the last upload" say "This is the first upload of this package to Debian, and here is that bit of changelog".

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information