Use UniformRNG as default template variable name for RNGs
Use rng as standard name for UniformRNG variables
Discrete distribution that offers a range-based equivalent of dice

This is adapted from Chris Cain's RandomDie submission to Phobos
in https://github.com/D-Programming-Language/phobos/pull/1702

The alternative name is chosen by analogy to Boost.Random and the
C++11 standard.
Correct author information for std.random2.distribution
Doc paragraph explaning function vs. range choice for distributions