Remove *nix platform dependency from development tooling

[kasparsd]

The current local development tooling requires bash, grep, awk and other unix specific tools to be available on the host machine.

Most of the commands defined under /bin can be moved into npm scripts that are cross-platform and have Node.js as the only dependency.

• This is a WordPress specific software library so our primitives are PHP, JS and web technologies in general. We should try to use those for scripting needs, too.

• Using JS scripts for development tasks ensures we can use the same linting and coding standards as the rest of the project. We get automatic error checking, etc.

• Scripts that can't be replaced without a lot of development effort (like tag-built.sh) could be run inside the Docker environment instead.

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