Reduce code reuse in inits

[MartinuzziFrancesco]

The deterministic initializers have a lot of structures in common. I think we can reduce code reuse by building functions such as

function delay_line!(reservoir_matrix::AbstractMatrix, weight::Number)
    for idx in first(axes(reservoir_matrix, 1)):(last(axes(reservoir_matrix, 1)) - 1)
        reservoir_matrix[idx + 1, idx] = weight
    end
    return reservoir_matrix
end

This way we can even have more control over the weights by having a dispatch over a vector of values

function delay_line!(reservoir_matrix::AbstractMatrix, weight::AbstractVector)
    for idx in first(axes(reservoir_matrix, 1)):(last(axes(reservoir_matrix, 1)) - 1)
        reservoir_matrix[idx + 1, idx] = weight[idx]
    end
    return reservoir_matrix
end