Add muntidim sbg input generation.

Currently the input for SBG binary eval only handles one dimension. Extend with the previous code for multi--dim intervals.
```
void GenerateSBGInput::addDims(size_t max_dim, size_t exp_dim, SBG::MultiInterval& intervals, int offset)
{
if (max_dim > exp_dim) {
for (size_t i = exp_dim; i < max_dim; i++) {
Interval interval(offset, 1, offset);
intervals.addInter(interval);
}
}
}

void GenerateSBGInput::addDims(size_t max_dim, size_t exp_dim, ORD_REALS& constant, ORD_REALS& slope)
{
ORD_REALS::iterator constant_it = constant.end();
ORD_REALS::iterator slope_it = slope.end();
if (max_dim > exp_dim) {
for (size_t i = exp_dim; i < max_dim; i++) {
constant_it = constant.insert(constant_it, 0);
slope_it = slope.insert(slope_it, 0);
}
}
}
```

```
int GenerateSBGInput::generatePWLMaps(Expression exp, int offset, std::string eq_id, size_t max_dim, IndexList dom, int edge_id)
{
.
.
.
if (indexes.empty()) { // Scalar variable.
addOffset(edge_id, "M1", 0, node_id);
_m1_slopes.push_back(1);
addDims(max_dim, 1, constant_pwl_map_u, slope_pwl_map_u);
} else {
addDims(max_dim, indexes.size(), constant_pwl_map_u, slope_pwl_map_u);
}
for (const auto& idx : dom) {
Real set_vertex_init = getMin(idx);
addOffset(edge_id, "M2", 0, eq_node_id);
}
if (dom.empty()) { // Scalar variable.
addOffset(edge_id, "M2", 0, eq_node_id);
addDims(max_dim, 1, constant_pwl_map_u, slope_pwl_map_u);
} else {
addDims(max_dim, dom.minElem().size(), constant_pwl_map_eqs, slope_pwl_map_eqs);
}
.
.
.
}
```