Set up Python develop environments

- use `pyenv` to manage the various develop environments
  + install several Python binaries
  + each environment receives its own `poetry` install
- add two virtual environments:
  + "interactive" => default environment with no library,
                     which receives accidental `pip install`s
  + "utils" => hosts various globally available tools/apps
               (e.g., `mackup`)
- add installation and update scripts

.profile

@@ -34,6 +34,11 @@ export BAT_CONFIG_PATH="$HOME/.config/bat/config"
 
 export LESSHISTFILE="${XDG_CACHE_HOME:-$HOME/.cache}/.lesshst"
 
+export PYENV_ROOT="$HOME/.pyenv"
+_prepend_to_path "$PYENV_ROOT/bin"
+# No need for *.pyc files on a dev machine
+export PYTHONDONTWRITEBYTECODE=1
+
 export PSQLRC="$HOME/.psqlrc"