Improve dev tools in the Nix environment (#1666)

* Improve dev tools in the nix environment

Added postgrest-build, postgrest-run, postgrest-clean, postgrest-check
and postgrest-watch tools. Changed order of postgrest-test-spec-all to
run backwards from pg13 to pg9.5. Added shellcheck to lint shell scripts
in nix environment.

Co-authored-by: monacoremo <monacoremo>

.circleci/config.yml

@@ -10,7 +10,7 @@ jobs:
       - checkout
       - run:
           name: Install linting and styling scripts
-          command: nix-env -f default.nix -iA devtools
+          command: nix-env -f default.nix -iA style
       - run:
           name: Run linter
           command: |