0.6.2: depolarizing channel error model, constant seeds

Added

depolarizing_channel error model and docs
ability to pass constant seed for deterministic simulation
RandomTest doing Kolmogorov-Smirnov statistical test to match random numbers with their ideal probability distribution

Changed

fixed docs
source files use .hpp/.cpp extensions
random number distributions (integer min/max and real 0-1) are done in-house for portability and consistency of results

Removed

nothing