metropolis_hastings: Instantiate metropolis_hastings object and set initial...
In JTT94/cpmmc:

This is an S3 object constructor helper function for class metropolis_hastings which inherit from markov_chain class

1 2	metropolis_hastings(initial_params, log_target_density, log_proposal_density, proposal_sampler)

`initial_params,`	numeric for initial state of chain, list for multiple named parameters
`log_target_density,`	the log target density for the MH algorithm, i.e. the log density for the stationary distribution of the Markov Chain
`log_proposal_density,`	log density function for parameter proposals
`proposal_sampler,`	distribution function to sample new parameter proposals