consolidate random number logic
Note, I suspect Rng::rollClosedProbability() is not needed. The only difference between it and rollProbability() is that one time in 37k (on Windows), it will give an output of 1.0. On some versions of Linux, the value of 1.0 will occur about 1 time in 4 billion.
Showing with 214 additions and 92 deletions