Marker interface for normalized Gaussian sampler

Given that

1. an N(0,1) sampler is a building block for several other samplers
2. there are multiple implementations for sampling from an N(0,1)

it is proposed to create a NormalizedGaussianSampler interface (that extends ContinuousSampler).

Then, a new GaussianSampler class can be defined, that will sample from an N(mu,sigma), whose constructor's argument will be

• NormalizedGaussianSampler
• mu
• sigma

An implementation of NormalizedGaussianSampler will be BoxMullerNormalizedGaussianSampler (and consequently the current BoxMullerGaussianSampler will be deprecated).