Add utility for constructing the operators used by a discretization emplying RV-stabilization - Add constructDiffOps which creates the operatores used for a scheme with RV-stabilization - Minor clean up in RungekuttaExteriorRV

function s = stuffStruct(varargin)
    s = struct();

    for i = 1:nargin
        assert(~isempty(inputname(i)), 'All inputs must be variables.');
        s.(inputname(i)) = varargin{i};
    end
end