random functions should use generic pseudo-random generators

[arashbm]

Currently some functions use integer seeds, while some others use a mix of std::mt19937 and std::mt19937_64. The code should allow the use of a generic pseudo-random generator or at least use one uniformly, which is bad for reproducibility and backwards compatibility reasons.

[arashbm]

Currently the last places that use hard-coded uniform random bit generator are the exponential and geometric temporal adjacency types.