[Maybe] Give error if a project without 'api' has 'requires transitive' entries

[jjohannes]

For example, if the src/main/module-info.java of an application project contains requires transitive ...; entries.

Right now, these entries are silently ignored.

Note: Not sure how to solve this yet. The dependencies are lazily created for each configuration (scope). The scopes do not know about each other and there is no central place where all scopes are known. If one scope does not exist, there is simply no one reading the corresponding requires. This would need some kind of extra check mechanism.