Change metadata parameter and several code improvements

[miguelaeh]

Description of the change

This versions includes a mjor change since the default parameters have been changed. --metadata has been substituted by --schema

Benefits

Improves code and options names

Possible drawbacks

Applicable issues

• fixes #

Additional information

Checklist

• [x] Version bumped in package.json and package-lock.json according to semver.
• [x] New features are documented in the README.md
• [x] New features contain a new test at the tests folder
• [x] All tests pass running npm test