Hydrilla

fix "no translation file found for domain" error

change translation domain to 'hydrilla-messages'

enable using with Python 3.7

make "uuid" an optional property

specify full schema URL in instances

when generating JSON documents, put generating software info in 'generated_by' property

move locales under builder/

expose the entire translation object instead of just its gettext method

internationalize using Babel

this commit also makes the sdist tarball generated by setuptools REUSE-compliant

bump schemas subrepo to a8442778ff400fd9d50cac7944b491c7d641df1f