new_set: Create new parameter set
In bobverity/rmaverick: Analysis of population structure

Create a new parameter set within an rmaverick project. The new parameter set becomes the active set once created.

new_set(
  project,
  name = "(no name)",
  lambda = 1,
  admix_on = FALSE,
  alpha = 0.1,
  estimate_alpha = TRUE
)

`project`	an rmaverick project, as produced by the function `mavproject()`
`name`	the name of the parameter set
`lambda`	shape parameter of the dirichlet prior on allele frequencies in each subpopulation
`admix_on`	whether to allow admixture between subpopulations, in which case each gene copy can be assigned to a different subpopulation
`alpha`	parameter governing the strength of admixture. Higher values give greater probability of a gene copy being assigned to different subpopulations, while as alpha tends to zero we converge back at the no-admixture model in which all gene copies within an individual are constrained to have originated from the same subpopulation
`estimate_alpha`	whether the value of alpha should be estimated as part of the MCMC, in which case the value `alpha` is ignored