v0.3.1

Fixes to installing either script. Nothing changes in what the functions send or return, apart from the version.

• Both scripts install into a schema whose name needs quoting, such as "ML Funcs" or "Analytics". They
  failed with invalid name syntax or schema "analytics" does not exist.
• Installing sql/drex_http.sql into a second schema no longer breaks an install in the http extension's schema
  (such as public). It dropped that install's _drex_settings(), so every call to it failed with
  function _drex_settings() does not exist.
• Requests identify themselves as drex-postgres/0.3.1 and drex-postgres-http/0.3.1 in X-Nace-Client.

Install: git clone --branch v0.3.1 https://github.com/nace-ai/drex-postgres.git, then follow the README. To upgrade from 0.3.0, check out v0.3.1, reinstall the package (PL/Python variant) and run the same script again.