Check for Java compatibility

[rvanheest]

Since this library is not only meant for internal use, but also for external customers who wish to create a bag to be deposited at DANS, this library should work with Java as well.

Write a number of demo applications in Java that cover all features of this library. Check if they are all compatible and report any issues with it.
Make sure they either can be checked by the compiler or can be ran as tests.