Missing import when generating code from a model with an implementation class

[Céline Bensoussan]

The implementation class java.lang.reflect.Method is not being imported by the Java code generator when it is used in a model.

[Matthias Schoettle]

The same problem exists when using a class java.util.concurrent.BlockingQueue.

[Matthias Schoettle]

java.lang classes are excluded, but actually might need to be imported.

[Matthias Schoettle]

Resolves #408: Removes exclusion of java.util and java.lang imports.

Ensures that no duplicate imports are generated.

→ <<cset aa11623e94e1>>