Make the level of detail the scan of external classes provides configurable

[StephanPirnbaum]

The jQAssistant Java Scanner currently only provides a shallow node for referenced classes when they are part of externally referenced libraries and not part of the scan path.

With jqassistant-archive/jqa-maven3-plugin#10 it is possible (in Maven projects) to specify what external libraries should be fully scanned. However, this imposes a large impact on the performance while the level of detail the full scan provides is mostly not required.

What is required, though, are often only information about the class hierarchy for e.g. Exception or List implementation in the JDK or base classes like Repository in the Spring Framework.

With that, I propose to introduce a configuration for the level of detail of scans, i.e.:

• Default - As is, classes that are on the scan path are fully scanned, library classes are created as a shallow node
• ClassHierarchy - As Default, but including the full inheritance hierarchies (including generics) of library classes
• ClassAndMethodHierarchy - As ShallowHierarchy, but including method declarations

I currently don't have a proper name for the levels but I think this at least gives an idea.