Improve handling of missing project.basedir property

The cargo.run profile in the main pom of an archetype-built project has a system property project.basedir. Before Essentials you could remove this property to disable automatic export. Now also webfiles relies on this property.

But when you remove the property Essentials cannot work properly either. But it is not dealing very well with this situation. The log explodes with huge stacktraces and the Essentials app shows errors and reports that the system is down, while it actually isn't.

Just one warning in the logs would suffice, and the webapp could show this warning as well.