1. Refactored Nix devshell/package to make it easier to keep
LD_LIBRARY_PATH & buildInputs in sync (plus make it easier to re-use
in other Nix environment).
2. Added a CI job to ensure that Blueprints are formatted correctly and
that they will compile using `blueprint-compiler` 0.16.0.
3. Reformatted all Blueprints with `blueprint-compiler format`.
