New lint test: schema param description

[ewels]

I can't think of a time when it's ok for a parameter in a schema to not have a description. So we should probably lint for that and throw a warning.

Also warn if there are any ungrouped parameters.

[KevinMenden]

Looking into this, I realized that the lint tests are not self-contained. Meaning one only runs when the other has been run before.
That's pretty dangerous, and in fact you can easily break it when running only nf-core lint <pipeline> -k schema_params

So we should probably make that more robust/ the tests self-contained.

[ewels]

Yes, good point with the -k. You mean stuff like getting the pipeline config?

[KevinMenden]

Yeah creating the schema object, the error was easy to catch because we basically have a comment saying that:

tools/nf_core/lint/schema_params.py

Lines 19 to 23 in dc5288d

	# First, get the top-level config options for the pipeline
	# Schema object already created in the `schema_lint` test
	self.schema_obj.get_schema_path(self.wf_path)
	self.schema_obj.get_wf_params()
	self.schema_obj.no_prompts = True

[KevinMenden]

Remnants of the old code structure I guess