Implementation for "Copy Qualified Name" (#1001257)

This is a first implementation for "Copy Qualified Name". The GUI interacts with ScalaCopyQualifiedNameAction, with extends and eventually delegates to the corresponding Java class. The actual works happens in NamePrinter.

I'm still planning to do some tweaks/changes/feature additions, but I wanted to share this with you early.
Does `compiler.enclosingValOrDef` do what you need?