Allow to parameterize the server id for POM repositories

[kwin]

In case of POM repositories only the credentials are being maintained in the settings.xml. In order to support that use case better it would be helpful to optionally allow to parameterize the server id (as it must match the repository id from the pom.xml). In such a case the repository URL doesn't need to be populated obviously (because it is contained in the POM repository).