Add dstats.random.rUniform as Overload of std.random.uniform

[jmh530]

dstats.random does not currently have its own uniform random number generator. It relies on std.random.uniform.

We can add a rUniform function that in turn calls std.random.uniform and change calls to uniform to calls to rUniform. Then, if dstats decides to switch to an alternate random number generator, one only needs to change that function.