Generate random value using different distributions

[phimage]

a RandomDistribution enum to describe the type of distribution

• a protocol RandomDistribuable implemented by Double and Float
• functions to generate random values using specific distributions

a DiscreteRandomDistribution enum to describe the type of discrete distribution

• a protocol DiscreteRandomDistribuable implemented by Int and a type to generate probability BernoulliProbability implemented by Double
• functions to generate random values using specific discrete distributions

Unit tests

• assert on well known mean and/or variances

[nvzqz]

Because Foundation is available for Linux, can you please use Foundation imports rather than Darwin and Glibc.

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I have done it except in new class in unit test
but test could be launched also on linux so I must change that