Add a get_critpath_packages to PackageListing
Add a create_package_critpath method for the unit-tests
Test the Packagelisting.get_critpath_packages
Add a boolean to mark a package as critpath when creating it
Add a get_critpach_packages in the internal API

- Include unit-tests for this method
Fix unit-tests for when adding a package specify the critpath
Typo in the API collections documentation

Thanks to RemiFedora for pointing it out
Remove un-used form
Add a new endpoint in the extras API the /api/critpath endpoint

- Add corresponding unit-tests