Integration methods and discretization of normal distributions

• legendre: Calculates Gauss-Legendre nodes and weights
• normal_discrete (one-dimensional): Discretizes a one-dimensional normal distribution into nodes and weights
• normal_discrete (two-dimensional): Discretizes a one-dimensional normal distribution into nodes and weights
• log_normal_discrete (one-dimensional): Discretizes a one-dimensional normal distribution into nodes and weights
• log_normal_discrete (two-dimensional): Discretizes a one-dimensional normal distribution into nodes and weights
• discretize_AR: Discretizes a AR(1) process with normally distributed innvoations