Check schema against meta-schema

[ewels]

It would be nice if nf-schema could validate the pipeline nextflow_schema.json against the nf-schema parameters_meta_schema.json. If there are any failures these can be logged to the console as a warning (non-blocking).

This will require the meta-schema to be kept up to date, but that's no bad thing as we're hoping to use it elsewhere as well anyway ('cc @mashehu).

[awgymer]

Do we have an analogous meta schema for the samplesheet schema? Or is that currently just assumed to be able to be any valid draft 2020-12 schema?

[nvnieuwk]

For now all schemas are assumed to be 2020-12 schemas :) But the meta-schema will be used to validate the parameter schema in the future