Refactor TestViewFactory to Java

[JanWittler]

Refactors the TestViewFactory to Java as otherwise it cannot be used by other Java classes.
The code is pretty much a duplicate of the Xtend code but we might discuss whether we want to explicitly throw exceptions (as it is implemented right now) or reuse the sneaky throw mechanics of Xtend (i.e. the Exception is not declared and thus needs not to be catched explicitly). I selected the former approach to have the Exception semantics explicit but one might argue that, as it is only for testing purposes, not having to catch the exceptions might make the test code easier to write. In the end, the current design results in any view-based test method declaring a throws Exception in its signature.