Blurb:: Sequence of sparse grid levels used in a multi-stage expansion

Description::

Each level entry of the \c sparse_grid_level_sequence applies to one
expansion within a multi-stage expansion.  Current multi-stage
expansions that support sparse grid level sequences include multilevel
polynomial chaos, multifidelity polynomial chaos, or multifidelity
stochastic collocation expansions.

If adaptive refinement is active, then this sequence specifies the
starting point for each level within either an individual or
integrated refinement approach.

A corresponding scalar specification is documented at, e.g.,
\ref method-polynomial_chaos-sparse_grid_level

Topics::
Examples::
Theory::
Faq::
See_Also:: method-polynomial_chaos-sparse_grid_level
