Gaussian regime models

Toolset regime_gaussian: 3 tools.

Tool	What it does	Notes
`regime_gaussian_hmm`	Gaussian hidden Markov model (Baum-Welch) on a returns series or feature table, one or several sequences.
`regime_gmm_hmm`	Hidden Markov model whose regimes each emit from a mixture of n_mix Gaussians (fat-tailed, skewed or multi-modal returns within a regime).
`regime_variational_gaussian_hmm`	Variational Bayesian Gaussian hidden Markov model: Dirichlet, Normal and Wishart priors, fitted by maximising the variational lower bound.

Inputs, limits and outputs are described in Fincept Regimes. Full schemas: fincept_describe_tool.