Compatibility with TDBjava

[Cimbali]

In recent years, the java TDB has received more love than this version, the C++/Qt TDB 2 (mainly due to @tdeo's inability to cope with C++).

Now I'm up for occasionally maintaining this code, but we have to decide whether we want to keep both versions compatible, especially regarding databases. Since the database model used in the other TDB has changed a couple times and hasn't been versioned afaict, this would require some coordination.

So thoughts on the question? Comply or split? Some database updates like storing every transaction twice are dubious.