JDK classes should also be scanned if required

[cristalp]

Started by #1995

The Maven plugin doesn't scan any JDK classes. We use TimeUnit in some REST endpoints, and while there is a workaround for that (thanks @MikeEdgar), it's cumbersome.

So I suggest an enhancement: Either there should be a flag to enable JDK class scanning or there should be a plugin property where a number of JDK classes can be listed to be scanned.

Since the first solution would probably make scanning slower, I suggest implementing the second solution - thanks!