Auto checking with versioned projects doesn't work

[davesproson]

We can now register a project with vocal so that we can simply run vocal check myfile.nc without having to explicitly give the project/definition.

This fails if the project points to a 'versioned' folder (i.e. with a conventions.yaml and version subdirectories). This needs fixing either explicitly in the check script, or more generically by dealing with this in import_project.