=> portfolio optimization: extend vignette and examples
=> doc: stepAIC.ghyp
=> q/p.default: warn only once
=> Student-t: use Gaussian if, e.g., dof >= 1e5
=> vignette: describe stable property of NIG.
=> Use \texorpdfstring{TEX text}{Bookmark Text} in vignette for parametrization subsections.
=> Handle NA's in multivariate fits by using EM imputation
