CLI for managing the contract / crates

Commands:

• build: build the contracts to /target directory. Unless --package [pkg_name] is specified, all contracts will be built. Add --docker to run from the parity contracts-ci image. Add --package [pkg_name] to target a specific crate/contract.
• test: test all crates and contracts. Add --docker to run from the parity contracts-ci image. Add --package [pkg_name] to target a specific crate/contract.
• fmt: format all crates and contracts. Add --docker to run from the parity contracts-ci image. Add --package [pkg_name] to target a specific crate/contract.
• clippy: run clippy on all crates and contracts. Add --fix to have clippy auto-fix any issues it detects. Add --docker to run from the parity contracts-ci image. Add --package [pkg_name] to target a specific crate/contract.
• chown: take ownership of the /target and /contracts directories, as running commands in docker mode may have changed them to belong to the root user (this is an issue with parity's contract-ci image - nothing we can do about it right now)
• expand: expand a contract. This takes any macro calls/attributes and unwraps them using cargo-expand. This is helpful for seeing the output of a macro. Add --package [pkg_name] to target a specific crate/contract.
• metadata: generate the metadata for a contract. Sometimes cargo gets stuck on this, so it's helpful to be able to run it directly to observe the error. Add --package [pkg_name] to target a specific crate/contract.

Run the above commands using npm run cli -- <command> <args>. E.g. to build the captcha contract in release mode, run

npm run cli -- build --package captcha --release