Fix getRandomNumber to also return negative real values.
Fix getRandomNumber to also return negative real values.

The old implementation only returned values in range [min, max), with
min the smallest number >0, max the greatest real value.
Change to return values in range [lowest, max), but with double the
distance between each possible value. The std real distribution does not
support to return any rela value in range [lowest, max) with smallest
possible distance between real values.

pjgeorg/pMR,pjgeorg/pMR,pjgeorg/pMR