Instead of deriving from cNumberGenerator, models now use a distinct RNG
in the global RNG array. This ignores the user specific mapping, but
introduces a mapping that creates <num-rngs> RNGs per module and maps
them accordingly.

This solves the problem that RNGs could not be called from inside a
module before.

You may need to change your models and you'll have to update the example
model as well!