miniwdl check does not enforce parameter_meta requirements per spec

[aofarrel]

The WDL spec notes that although parameter_meta is optional, any keys that it does have must correspond to a task input or output.

miniwdl check does not enforce this, so it's easy for someone foolish (it's me, I'm the fool) to forget to update the corresponding parameter_meta value when I rename an input value.

I'm not completely sold on womtool's approach of considering a parameter_meta mismatch to be an error, but I think it would be appropriate to have miniwdl check at least throw a warning. This would also help ensure compatibility across the two executors.