Domain type mingling

[gchabert]

When initializing a domain, the actual dimension of the argument should be taken into account and not only the object type as the domain resulting type is calculated from the dimension. For example, the following program is correct and crashes. A clear spec for Domain is just missing maybe.

   IntervalVector x(1,Interval::PI);
   Domain d(x,false);
   cout << d.dim.is_scalar() << endl;    // displays "true"
   cout << d.i() << endl;  // d.v() actually incorrect... (as specified ?)

[gchabert]

Just added some asserts in the code + fix in ExprConstant