General constraints vs box constraints in DMS package

[markusgft]

Currently, the DMS-package does not distinguish between box constraints of form

u_lb <= u <= u_ub and x_lb <= x <= x_ub,

and general constraints of form

d_lb <= g(x,u) <= d_ub

When setBoxConstraints() is called in the DMS Constraint Discretizer, all box constraints are mapped back to general inequality constraints.

Treating them explicitly as box constraints might be advantageous in some cases.