Remove the need for unrolling and allow real loops

[zimmski]

Unrolling is currently in place to work around the complexity of real loops in the token graph. But this also means that recursive defined formats are not really recursive but have an finite end which is not only bad for generating big data but also for reading in data since the maxRepeat variable (which controls the depth of unrolling) has to be set accordingly.

This does mean that unrolling AND real loops have to be implemented side by side. Removing unrolling is not an option since it has advantages too. But maxRepeat=0 (== real loops) should be the default after implementing real loops.