update json-schema template to new structure

* Check that we have at least 1 parameter, fail if not
* Log number of parameters found

* Use 'pipeline schema' instead of 'JSON Schema' in logging
* Work with top-level schema and defintions sub-schema
* Strip out logic about object-type properties
* Test nf-core schema build with dummy pipeline

Also update all pytest.mark.xfail to use strict=True, so fails if an exception is not raised.

Switched from https://nf-co.re/json_schema_build to https://nf-co.re/pipeline_schema_builder

…schema params

Check for presence and values of top-level $schema, $id, title and description

New-new schema