Reshaping repo

The repo is designed for use with an existing builds.sr.ht service.
Besides lacking that, I am more interested in a containerized workflow
powered by a Makefile. Package source code will live in `pkgsrc/`,
packages will be built into `pkg/`, and packaging keys will be
generated into `keys/`.

Alos trimmed the packages down to what I will build.

py3-*: reset pkgrel

py3-*: bump pkgrel for python rebuild

py3-*: bump pkgrel and update upstream versions

Update all non-sr.ht Python packages

py3-intervals: upgrade to 0.9.1

py3-intervals: bump pkgrel

sr.ht/py3-intervals: bump pkgrel

Update all dependency packages

Set all pkgrels to zero

Move into subdir for abuild reasons

Add py3-sqlalchemy-utils and friends