This function uses a dependency graph created with
makeDepGraph to list all (recursive) dependencies of a
given package in an order suitable for installation.
getInstallOrder(pkg, depG, needed.only = TRUE)graphNEL instance as returned from
makeDepGraph.
TRUE, only those
dependencies not currently installed are included in the list,
this is the default. When FALSE the complete list of
dependencies is given regardless of the set of currently
installed packages.