Add all known outstanding yaml config options as of process-compose v1.7.3 (#98)
* Add all known outstanding yaml config options as of process-compose v1.7.3
- per-process `description` that displays in the UI
- global and per-process `log_configuration`, including `rotation`
- global and per-process `vars` for supporting Go template expansion on configs
- `env_cmds` allows running host commands to populate env variables
- `ordered_shutdown` controls the order of process shutdown
- `is_strict` does additional checking on configuration files at startup
- `disable_env_expansion` to not propagate .env variables to processes
- `http_get.{headers,status_code}` and `working_dir` for probe commands
- `replicas` to run multiple copies of processes
- `entrypoint` alternate to `command`
- `is_elevated` for sudo/runas priviledged processes
- `extends,is_disabled,is_dotenv_disabled` for multi-file fragments and overrides.
- `launch_timeout_seconds` for daemon processes
* new: add additional PC_ env variables
- Make disable-dotenv default to true, per @adrian-gierakowski request.
- Remove unnecessary args in vars.nix
* fix: import of vars.nix needs no extra args now