[MNG-6131] Support pom without coordinate

**[Robert Scholte](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=rfscholte)** opened **[MNG-6131](https://issues.apache.org/jira/browse/MNG-6131?redirect=false)** and commented

In some cases the GAV is only there because Maven expects it, even though these coordinates will never be used.
The most common case is an aggregator: it will only trigger module without being part of a multimodule project.
Another case I'm thinking of are test-cases, where you want to show the behavior of some plugins. This project self will (or should!) never be installed or deployed.
In general: the GAV is only required when another project will refer to it or if you want to distribute the project via a M2-repository manager.

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No further details from [MNG-6131](https://issues.apache.org/jira/browse/MNG-6131?redirect=false)